Screening For Good Health: The Australian Guide To Health Screening And Immunisation

By Dr Kerry Kirke, Dr Nicola Spurrier and Mr Martin Bray

Screening for Good Health is a practical guide to help you make sense of the hundreds of health messages that we are bombarded with each year. Whether or not there is a family history of a particular illness, screening and immunisation are smart, simple steps anyone can take to counter preventable diseases.

Prepared by experts in their field, Screening for Good Health gives an overview of the stages in life, the screening tests and immunisations that are relevant to each age bracket, and the importance of your own record-keeping.

An alphabetical listing covers every illness from Alzheimer’s Disease through to Osteoporosis to Tuberculosis. For each preventable illness, the entry provides up-to-date information on:
- its symptoms
- risk factors
- disease progression
- protective lifestyle choices an individual may consider
- the screening tests available
- the health services at your disposal, and
- the treatment available.

Also included is a comprehensive travel health section, with a convenient checklist covering all aspects of health protection during travel, and a first-aid guide.

• Language: English
• Publisher: Melbourne University Publishing Ltd
• Release date: Jul 1, 2009
• ISBN: 9780522859331

Book preview

Screening for

Good Health

Screening for

Good Health

The Australian Guide to Health Screening and Immunisation

MARTIN BRAY

DR KERRY KIRKE

DR NICOLA SPURRIER

WITH DR RICHARD WILSON AND DR CHRIS HOLMWOOD

Contents

Acknowledgements

Introduction

Emergency First Aid: Resuscitation, Heart Attack, Allergic Reaction, Stroke, Snake and Spider Bites

Part 1   Screening and Prevention

Why Screen? When Is Screening Good Practice?

Costs versus Benefits

Defining Normal and Abnormal

Family History

Genetic Inheritance

Genetic Testing

Screening and the Law

The Delivery and Affordability of Disease Prevention Services in Australia

Minimising Out-of-Pocket Costs

Your Immune System

How Does Vaccination Work? Why Do Some People Avoid It?

The Prevalence of Vaccine Preventable Diseases in Australia

The Australian Vaccination Program

Cancers—An Overview

Australian Cancer Statistics

---

Part 2   Life Stages

Age Group Recommendations for Health Screening and Immunisation

Pregnancy

Early Childhood

Young Adult

Middle Life

Older Age

Record Keeping

---

Part 3   Alphabetical Listing

Alzheimer’s Disease

Antenatal and Postnatal Depression

(Abdominal) Aortic Aneurysm

Australian Bat Lyssavirus Infection

Bird Flu (Avian Influenza)

Bowel Cancer

Breast Cancer

Cardiovascular (Heart) Disease

Cervical Cancer

Chickenpox (Varicella)

Chlamydia

Cholesterol

Dental Health

Diabetes

Diphtheria

Foetal Abnormality

Glaucoma Vision Loss

Growth—Children

Haemochromatosis (Iron Storage Disease)

Helicobacter Pylori and Stomach Cancer

Hepatitis A

Hepatitis B

Hepatitis B Screening

Hepatitis C Virus (HCV)

Hib

HIV

Hypertension (elevated blood pressure)

Influenza

Kidney Disease

Lung Cancer

Macular Degeneration (Vision Loss)

Measles

Meningococcal Disease

Mesothelioma

Mumps

Newborn Babies—Deafness

The Newborn Physical Examination

The Newborn Screening Test

Osteoporosis

Ovarian Cancer

Parkinson’s Disease

Pertussis (Whooping Cough)

Pneumococcal Disease

Poliomyelitis

Preschool Children: Development, Vision and Hearing

Prostate Cancer

Q Fever

Rhesus Negative Blood Group Screening

Rotavirus

Rubella

Rubella Immunity Screening

Sex Hormone Levels

Skin Cancer

Sudden Cardiac Death in Young Adults

Syphilis Screening

Testicular Cancer

Tetanus

Tuberculosis

Vitamin D Deficiency

---

Part 4   Travel

Travel Preparation

Traveller Risk Reduction Practices

The Complete Travel Health Checklist

Malaria Travel Medication

Cholera Travel Vaccination

Hepatitis A Travel Vaccination

Japanese Encephalitis Travel Vaccination

Plague Travel Vaccination

Rabies Travel Vaccination

Tick-Borne Encephalitis Travel Vaccination

Meningococcal Disease Travel Vaccination

Tuberculosis Travel Vaccination

Typhoid Travel Vaccination

Yellow Fever Travel Vaccination

Index

Acknowledgements

The authors would like to acknowledge the contribution of the following people:

Dr Peter Birdsey, General Practitioner, of McLaren Vale, South Australia, for encouragement to initiate this project.

Dr Chris Holmwood, Senior Consultant, Drug and Alcohol Services, South Australia, for the original planning of the content and for writing the first drafts of several topics.

Dr Robert Hall, past director of the Communicable Disease Control Branch, Department of Health, South Australia, for advice on the content and structure of the immunisation topics.

Dr Ann Koehler, Director, Communicable Disease Control Branch, Department of Health, South Australia, for advice on the topic ‘Reported Cases of Vaccine Preventable Diseases in Australia’.

Dr G Anthony Ryan, past director, Road Accident Research Unit, University of Western Australia, for an overview of the content and for reviewing most of the background topics.

Dr Wendy Scheil, Epidemiology Branch, Department of Health, South Australia, for reviewing the topics on avian influenza, TB testing and most of the background topics.

Professor Anthony Scott, Melbourne Institute of Applied Economic and Social Research, for commenting on the Delivery and Affordability sections.

Associate Professor Robert Bryce, Department of Obstetrics and Gynaecology, Flinders Medical Centre, for reviewing the pregnancy topics.

Dr Katherine MA Lyons-Reid, General Practitioner, of Bellevue Heights, South Australia, for a review of the chapters of relevance to middle life.

Dr Allan Calvert, Cardiologist, of Onkaparinga Hills, South Australia, for reviewing chapters related to cardiovascular disease.

Dr David Elder, Urologist, of Clarendon, South Australia, for reviewing the chapter on prostate cancer.

Associate Professor Craig Whitehead, Flinders University Department of Rehabilitation and Aged Care, and Senior Staff Specialist, Repatriation General Hospital, for a review of the chapters of relevance to older age.

Dr Anthony Gherardin, National Medical Advisor, Travel Doctor—TMVC Group, for reviewing the Travel section.

Dr Stephen Hedger, Head of General Medicine, Flinders Medical Centre, and Senior Lecturer, School of Medicine, Flinders University, for the review of some key general medicine topics.

Shannon Kolak, of St John Ambulance Australia, for developing a concise chapter on current first aid recommendations, with special emphasis on heart attack and stroke.

Foong Ling Kong, Executive Publisher, Melbourne University Publishing, for being prepared to give this concept a chance in the market without compromising the content, and for providing guidance in writing style and structure.

Sally Moss, of ConText Editorial, for final editing of the manuscript.

Full responsibility for any opinions expressed in this book rests with the author of each topic. The above people, who gave their time generously to this project, do not necessarily agree with all viewpoints expressed in any other part or under any subheading where they have not had the opportunity of direct input.

Introduction

We all worry about our health from time to time. Sometimes this is in response to some symptoms that we have. At other times, we just wonder whether we are doing everything we possibly can to stay well, especially when we hear about someone else who has a serious illness.

This book supplies readily accessible information on preventative health services that can be provided by the health care system before you have any symptom of a disease. These preventative health services can be advice, immunisation or screening tests.

An illness is not discussed in the book if it cannot be prevented by immunisation or does not have some future potential for useful early treatment if detected by screening before symptoms occur.

You may need this book because you ‘don’t know what you don’t know’. These key questions will help you determine what you don’t know:

Should I have a check-up?

How important to me as an individual are the health related topics I hear about in the media?

Can I be sure I have heard of all the preventative services available to me?

What tests, vaccinations or other health services would it be wise to have at my age (or before I travel), or for my children or elderly parents to have at their stage in life?

Are screening tests really all that important and do they make a real difference?

Many preventative tests, vaccinations and other services can be beneficial. But deciding which ones are useful to you at your stage of life can be difficult. The information that the community has in this area can appear conflicting and confusing, partly because the many recommendations are often updated.

Then there are some health providers and lobby groups that unashamedly pursue their own interests but act under the guise of ‘working for your best interest’ in providing information. The viewpoints of various professional groups may also differ as they see disease and illness in different ways. Finally, some services have not yet been shown to improve the lives of people receiving them (see the following box).

The PSA test–a controversial issue

The case study called Malcolm’s Story in the Prostate Cancer topic serves well to highlight the controversy surrounding many aspects of screening. The story, as recorded first hand from the patient, is true to the last detail. Yet when considering the population as a whole, the PSA test that Malcolm had is not recommended as a screening test due to (as RACGP general practice guidelines put it) ‘lack of sensitivity, specificity and evidence of improved outcomes’. See the topic on prostate cancer to find out why the PSA test that was good for an individual may not provide such a clear-cut benefit for others.

It is clear that any decisions about what to do should be based on good evidence, not opinion, bias or anecdotal information. Sounds simple? In reality, it can be quite difficult to determine whether health suggestions we hear about are based on solid evidence.

The role of evidence in medical research

Health checks, tests and treatments (what we call interventions) are based on scientific principles. The use of antibiotics for treating pneumonia, aspirin to prevent heart attacks in high-risk people and mammograms to reduce (but not eliminate) deaths from breast cancer are accepted as worthwhile interventions. They are accepted because they are all based on evidence from scientifically designed research. When the research studies are done, their results are publicised in the scientific literature and at conferences. The methods used in the research and the findings are scrutinised by other researchers in a process called peer review. In many instances the studies are repeated in several centres to check that the findings can be reproduced. Then the findings are incorporated into suggested rules for doctors called clinical practice guidelines and are eventually (often after many years) accepted into mainstream medical practice.

The problem

The way a medical condition progresses (or its ‘natural history’) can be highly variable, and when we look at medical interventions we see that not all treatments work for all people. And to complicate things even further, just because someone undergoing treatment gets better, it doesn’t mean that the treatment actually helped. It may have; it may not have.

An example: when a child has a middle ear infection and is treated with antibiotics and then gets better, we cannot be sure that the antibiotics actually made the child get better. The child could well have got better without the antibiotics, due to a normal immune system response.

The solution

To work out whether a new treatment works or not, researchers undertake trials with large numbers of patients with similar conditions. They randomly place these people into two groups:

a group receiving no treatment or the old treatment

a group receiving the new treatment.

Screening for Good Health

If a large number of people receiving the new treatment get better and the group receiving the old treatment or no treatment don’t get better to the same extent, then it is likely that the new treatment has a real effect on the natural history of the condition. There are mathematical standard levels of probability that are accepted as ‘proof’ that the new treatment works.

The quality control

Doctors and scientists are a suspicious and competitive lot. The research is sometimes done again in different settings to make sure that the findings can be used across different populations and countries. The more radical the findings of the research (for example, if a cure was discovered for breast cancer that has spread to different areas of the body), then the more often the research is reproduced to verify the findings. In addition, the original research data is often made available for other researchers to look at and criticise, to check that the research was well designed and carried out. In other words, no funny business.

Evidence rules–is that test or vaccination worthwhile?

The same rules of evidence that are applied to treatments for diseases are applied to preventative activities because, as we shall see in Part 1, all activities have a cost. Does the evidence show that the benefits justify the cost?

In health care, sometimes the cost and benefit of an intervention are roughly equal, and there is no real gain. At worst, the net result is a loss, and people suffer needlessly.

Lack of evidence–problems with the publicity of initial finding

ORANGE JUICE MAJOR CAUSE OF

ROAD CRASHES

The use of initial findings instead of real evidence, for the cause of an illness or the effectiveness of a proposed treatment, can lead to media stories that are false–the facts as stated won’t stand the test of time.

Sure, the above headline sounds crazy, and it is a bit extreme, but it highlights the type of superficial logic often used in the media when discussing cause and effect in relation to medical or social issues. It serves to illustrate the need for real evidence based on random-controlled trials, or large-scale statistical surveys that can control for other variables that may interfere with the cause/effect being studied.

How could such a headline have any logic to it? Consider a completely imaginary set of statistics. Let’s say that 20% of young drivers involved in a set of serious accidents in Westville were found to have been using cannabis, according to blood test results. We can imagine a headline ‘Cannabis may be a factor contributing to road crashes’.

Now imagine a lifestyle nutrition survey of this group of crash drivers that showed that 30% had orange juice for breakfast. This makes orange juice an even more significant contributor to road crashes, very surprising and worthy of quite a big headline.

Let’s now study a large sample of young motor vehicle drivers from Westville, 38% of whom are found to be cannabis users. But hang on a moment: only 20% of crash drivers had used cannabis. Therefore a higher percentage of non-cannabis users are involved in accidents than the general population of drivers. Therefore cannabis use is not linked to road crashes. It’s not hard to imagine another headline:

NEW STATISTICS: NO LINK BETWEEN

CANNABIS AND ROAD CRASHES

So what does all this tell us about initial statistics and the way they are sometimes interpreted as evidence? First, the fact that 20% of crash drivers used cannabis simply tells us that 20% used cannabis–nothing else definitive can be said (just like 30% having orange juice doesn’t tell us much about orange juice and accidents).

We have not really established a link between cannabis (or orange juice) and accidents. We can say that cannabis influences some aspects of how we perceive things, and driving requires the ability to perceive possible consequences for various actions. Therefore there are grounds for a hypothesis that a link between cannabis and accidents may exist. But this has to be investigated–evidence must be found.

People in positions of authority sometimes qualify statements with the term ‘anecdotal evidence’. For example: ‘There is some anecdotal evidence that there may be a link between cannabis and accidents’. Anecdotal evidence is defined as one factor (cannabis) existing in connection with another factor (crashes), where despite suspicion, there has yet to be established a true cause and effect connection. We need to be suspicious of the release of purely anecdotal evidence: it may simply be publicity-seeking.

The real link between the suggested cause and the observed effect can be evaluated by doing some type of large trial that controls for all other factors so that a statistically significant result is obtained.

So what do we make of the second headline? Non-cannabis users are certainly overrepresented in the imaginary crash statistics when compared with the whole population of young drivers. But is this evidence that no link exists between cannabis and accidents?

Let’s examine what other factors might be operating. First, a rushed reporter facing a deadline did not stop to consider that if someone admits in a survey that they use cannabis, it does not mean that they drive while under its influence–they may be occasional users. Secondly, further research of the imaginary young driver population discovered that for most regular cannabis users, the cost of the drug severely limited the money left over for car expenses and petrol. Regular cannabis users actually had a low crash rate because they drove much less often, and drove older, cheaper and less powerful cars. Only 17% of all individual journeys by all young drivers actually involved driving after using cannabis–a very different story. Cannabis users are now slightly overrepresented in our imaginary accident statistics compared with the whole young driver population.

Lack of real evidence–not just an issue for the tabloid media

The hypothetical above is centred on the quality of evidence that may be used at times in the popular media, but the scientific community itself is by no means squeaky clean when it comes to careful and objective reporting of information.

In recent times, the highest profile case of faked evidence and flawed reporting concerned the US journal Science, which on 12 January 2006 officially retracted two papers by the South Korean scientist Hwang Woo-suk. Dr Hwang claimed to have derived patient-specific embryonic stem cells from adult cells. In December 2005, a colleague made the claim that the evidence was faked, and a report from experts at Seoul National University confirmed this. The stem cells had actually come from a cloned human embryo. Dr Hwang was not the only one involved: twenty-eight team members were under investigation.

Another case that received significant publicity concerned the Merck drug Vioxx. Data on increased risk of heart attack was left out of a report on the ‘VIGOR’ trial of Vioxx, published in the New England Journal of Medicine. On 8 December 2005, the journal alerted readers to concerns about the validity of the study. Merk had actually cited the journal article a number of times to show that Vioxx did not increase heart attack risk.

So, while in this topic we have stated the truth about the importance of real evidence in deciding if a medical test or treatment is worthwhile, sometimes practice falls short of what is ideal in theory.

Generally, the scientific community does a good job at finding evidence about tests and treatments, but accurate reporting can be a problem. Occasionally, when big money is involved –either as research funds or pharmaceutical profits–the integrity of the scientific process is lost, and even reputable scientific organisations may not tell us the real story. While some people may suffer needlessly because of this, we can take some comfort from the observation that it does seem that the truth eventually emerges.

You can take control

We have tried to bring together the latest available evidence on most types of preventative health services. A range of reliable sources has been used, all of which base their assertions on cited references leading back to evidence-based research.

Our intention is to give you the means to take control of your health options so you can maximise opportunities for useful preventative actions.

We hope that the information in this book is useful to you in sorting out the right health-related choices with the help of your doctor.

How to use this book

Part 1 is background information only on screening, immunisation, genetics, your immune system and cancer. Some of these chapters may be useful in better understanding the illnesses and issues discussed in the alphabetical section.

Go to the life stage in Part 2 that suits you or your family member to find topics relevant to your health. A detailed coverage of topics can then be found in Part 3, the alphabetical section.

Use the table on pages 63–5 if you want to search easily using particular disease categories (like ‘cancer’) or match a particular disease to all relevant life stages.

Part 4, the travel section, is completely separate–so travellers, go straight to it!

Internet search tips

To keep up to date with health issues, particularly where you have a special interest due to risk factors, try these ideas to find reliable information.

Go to the Australian Broadcasting Corporation at www.abc.net.au and use the ABC search facility to access health-related information from the online health pages service, radio program transcripts, and transcripts of TV programs such as Catalyst, ABC News and current affairs programs.

When using a search engine like Google, type in the key word(s) for the illness, along with the name of a reputable organisation such as ‘nhmrc’, ‘mja’, ‘csiro’, ‘cdc’ or ‘mayo clinic’.

Yes, we admit it

The word screening is used somewhat loosely in this book, in line with general community understanding that it means that a person is checking for a health problem in the absence of symptoms. The usual definition of health screening is something done to look for a problem in a whole community. When a doctor checks an individual for a potential problem, this is more accurately called ‘case finding’ or ‘self-screening’.

Current First Aid Recommendations

Recommendations for emergency first aid treatment improve over the years with continuing re-evaluation.

Courtesy of St John’s Ambulance Australia, we have used this book as an opportunity to provide some current basic first aid information on the following pages.

STROKE

The Cause

A stroke occurs when an artery taking blood to the brain becomes blocked or bursts. In most cases, this is the result of a clot at a part of an artery narrowed by long-term build-up of fatty deposits. As a result of a stroke, brain cells are damaged and functions controlled by that part of the brain become paralysed.

Paralysis of parts of the body or speech problems are common after a stroke. Although many people can make a good recovery, a stroke can be fatal.

Do not ignore a mini stroke

Sometimes the person will get warnings of a future stroke. These ‘mini strokes’ (also called Transient Ischaemic Attacks or TIAs) are due to a spasm of the blood vessels or are the result of a temporary blockage in the smaller arteries supplying oxygen-carrying blood to the brain. These are associated with the same symptoms as stroke but are temporary and do not cause long-term harm to the brain.

Medical attention should be sought urgently as a minor stroke could be a warning of a future major stroke. About 1 in 5 people with a TIA will have a major stroke within 3 months, and a large part of the risk occurs in the first few days. The treating physician will try to find the cause of the TIA, and organise treatment to lower the risk of another TIA or stroke source:www.strokefoundation.com.au

Signs & Symptoms

All the signs of both stroke and TIA may be any one, or combination of the following:

          Weakness or numbness or paralysis of the face, arm or leg on either or both sides of the body

          Difficulty speaking or understanding

          Dizziness, loss of balance or an unexplained fall

          Loss of vision, sudden blurred or decreased vision in one or both eyes

          Headache, usually severe and of abrupt onset or unexplained change in the pattern of headaches

          Difficulty swallowing

FAST test - an easy way to recognise the signs of a stroke

F facial weakness – can the person smile? Has their mouth or eye dropped?

A arm weakness – can the person raise both arms?

S speech difficulty – can the person speak clearly and understand what you say?

T time to act – call 000 immediately.

Too many people wait to see if the symptoms disappear instead of calling an ambulance straight away. Time loss is brain loss, and getting immediate treatment can be the difference between severe disability and making a good recovery after stroke. (National Stroke Foundation – Australia)

www.strokefoundation.com.au

Management of Stroke

1       Follow DRABCD (Danger, Response, Airway, Breathing, CPR, Defibrillation)

2       Call 000 for an ambulance.

3       Reassure casualty.

4       If casualty conscious:

•   support head and shoulders on pillows

•   loosen tight clothing (especially around the neck)

•   maintain body temperature

•   wipe away secretions from mouth

•   ensure airway is clear and open.

If casualty unconscious:

•   place in recovery position

Inability to communicate when otherwise alert can cause extreme anxiety in the casualty. Grasp both hands and ask the casualty to squeeze. Usually casualty will respond with one or the other hand. Then communicate by hand squeezes–one for yes and two for no. Be calm and reassuring.

Risk factors and prevention

People most at risk of a stroke are those who are elderly, have high blood pressure, smoke, have heart disease or diabetes or have previously had a stroke.

While there are several stroke risk factors that cannot be controlled (e.g. gender, age and family medical history), there are also many risk factors that can. You can reduce the chance of having a stroke by not smoking, eating a balanced diet, controlling your blood pressure and exercising on a regular basis. Medication and or surgery may also be necessary in helping to prevent a stroke.

This information is not a substitute for first aid training.

Learn First Aid with St John www.stjohn.org.au 1300 360 455

Part 1 Screening and Prevention

At some stage in life, most of us will hear that there is reliable evidence of a test to detect latent disease. Then our doctor tells us it’s not worthwhile. This is because other factors are involved in deciding on the merits of a test, whether we are considering individual cases or the community as a whole. There are the issues of cost versus benefit and of good practice in the application of a screening test. And ‘good practice’ brings in further issues, such as family history and what we should call ‘abnormal’ test results. The possibilities of genetic testing are becoming well known in the community, but the usefulness of this process is not as clear-cut as some might expect.

As well as covering the above issues, Part 1 also provides some concise background information on understanding genetic inheritance.

Many separate items from the broad fields of immunisation and cancer are covered later in this book (see Part 3). To help put these in context, Part 1 contains some background information on understanding immunity, which is relevant to both these fields of medicine. Statistics are provided showing the prevalence of cancers and of vaccine-preventable diseases, and questions that generate community interest are examined.

Screening and immunisation as forms of prevention can raise legal issues and questions of equity and affordability. Each is covered separately, from both a community and an individual perspective.

Finally, aspects of immunisation, and the affordability of health services, can be controversial issues. We summarise the observations and determinations of a range of senior medical professionals and academics, or senior academic economists, whose published work on these topics is referenced back to original research.

Why Screen? When Is Screening Good Practice?

Screening for some conditions is accepted as good practice, while for other conditions it is not. To understand why this is so, we need to look at the underlying theory behind screening.

Generally people are screened with the aim of improving outcomes through early diagnosis of their condition and the adoption of an appropriate course of treatment. In some cases, as in insurance medicals, screening is done for other reasons. With insurance medicals, screening serves to provide the insurer with a baseline health check, as many insurers will not insure against future costs arising from a condition that the person already has. In these cases, the insurance screening medical serves more to protect the insurer.

This topic deals only with screening for the purposes of improving health outcomes.

Disease, screening and treatment

First we need to understand the natural history of a condition and the effect of treatments on this. All diseases go through a process as outlined below.

The disease starts at some stage before it can be detected with any tests. Most diseases cause symptoms at some stage in their course. They can then be treated and this treatment may improve the outlook for the patient. However, for many conditions, diagnosis at the stage where symptoms occur is far too late. At this point, treatments do not make much difference to outcomes and certainly in many cases do not rid the patient of the disease.

The aim of screening is to detect the disease before it causes symptoms, with the assumption that this will improve the outcome for the patient, because early diagnosis and treatment make a difference. However, it must be noted that this is just an assumption and only in some cases does it turn out to be true. Unfortunately, in other cases, early diagnosis and treatment make no difference to the outcome.

Determining the ‘critical point’ of a disease

The idea of critical points in the natural history of a disease was first described in 1960 by George B Hutchison of Harvard University School of Public Health. A critical point is a point in the progression of a disease where treatment makes a difference to outcome. The three critical points are shown in the diagram below. If the only critical point where a treatment will make a difference is at 1, then early diagnosis through screening will not improve the outcome for the patient. If the critical point where treatment makes a difference is at point 3 then there is no point making an early diagnosis; you just wait for the condition to cause symptoms. Screening that does stand to be beneficial is for diseases with a critical point at point 2.

An example is cervical cancer screening. There is a natural progression from low-grade squamous intraepithelial lesions (LSIL) to high grade squamous intraepithelial lesions (HSIL) (pre-cancerous conditions of the cervix that do not cause any symptoms and are completely curable) through to cancer of the cervix. Before screening was available, cancer of the cervix was often diagnosed late, as abnormal bleeding doesn’t occur until the cancer has been present for some time. By this time the disease has often spread to deeper tissues and may be incurable. Cervical cancer screening detects LSIL or HSIL early on, at critical point 2, when the person has no symptoms and feels well. This enables effective treatment that cures the disease before it has turned into cancer.

Breast cancer screening through mammography is another example. Diagnosis through mammography before the patient or the doctor has found a lump, followed by current best practice treatment, improves outcomes. However, in the case of breast cancer, earlier treatment is no guarantee of a favourable outcome. Several large trials or research projects have shown that, in women between the ages of 50 and 65 years, about 30 per cent of deaths from breast cancer can be avoided through a comprehensive mammography program. What this shows is that for some women the critical point is at 2, while for other women the critical point was at 1 and their outcomes have not improved.

Risks from screening

So far we have looked at the benefits of screening. However, as well as benefits, all health care activities have a risk.

‘What risk can there be from a simple blood test?’ you may well ask. The problem is that few diseases can be diagnosed just from a blood test. Many require further testing to fully establish the diagnosis and these further tests can have significant risks. Take prostate cancer, for instance. Further tests after the prostate-specific antigen blood test require biopsy of the prostate gland and this biopsy has significant risks in terms of serious infection.

Even with a very good screening test, one of the perversities of testing large numbers of well people is that the vast majority of initial positive screening tests end up being false alarms. The initial screening tests are not diagnostic, as illustrated in the diagram below.

The definitive follow-up tests need to be done to confirm the diagnosis and in many instances they are negative. Most people with a positive screening test do not have the disease. They are therefore subjected to the risks of the follow-up tests with no extra gain. When this happens to large numbers of people the overall adverse outcome for all the people tested can be greater than the benefit for the few who had the condition in the first place.

The need for proper trials

It can be difficult to interpret research findings from screening studies. Early diagnosis can seem to result in longer survival after diagnosis, but in some cases this is just due to the fact that the disease has been found earlier. (The actual time between the onset of the disease and the final outcome is the same, it’s just that we are aware of the diagnosis for longer.)

The only way to know for sure that a screening program is beneficial is for it to be tried in a properly designed, randomised controlled trial. In these trials people are allocated to either a screening program group or a no-screening group and their outcomes are measured over years.

What this means for you

When we recommend screening tests in this book it is because there is good evidence that they make a difference to outcome: people live longer, are less disabled or require less noxious treatments because of the screening programs. Large screening programs involve expensive tests that have a potentially greater risk of causing some harm because we are applying them to large numbers of well people, so it is essential that we have good evidence that they work before unleashing them on an unsuspecting community.

Screening for prostate cancer is an example where such good evidence has been lacking. What has occurred as a result of the surge in popularity of testing for prostate cancer through the use of the prostate-specific antigen (PSA) test is that many men have been subjected to radical surgery and radiotherapy for cancers that may not have killed them in any case. (This is dealt with in more detail in the section dedicated to prostate cancer, page 299.)

What makes a useful screening test?

¹

A screening test is worthwhile when:

we are screening for an important and well understood health problem, where we know it can be present in a person in an early form without symptoms

we have a safe, simple and accurate test that has been shown to work well in detecting early disease

we have specific and widely agreed test values that are used to decide if a test is positive

there are effective treatments for any early disease that is found using the screening test

the benefits to people of the effective treatments outweigh any harm caused by the screening program

the screening and treatment program does not use up money that could save more lives and prevent more suffering if spent in other ways.

References

1   The Royal Australian College of General Practitioners, Guidelines for Preventive Activities in General Practice, 6th edn, 2005.

---

Costs versus Benefits

Screening

With ostensibly useful screening (where the disease critical point is at ‘2’), the risks and benefits need to be weighed up. Let’s start with an example.

Consider screening for bowel or colon cancer. The best method for detecting very early cancer is a colonoscopy. This is generally a very safe procedure, yet there is a small but definite risk of bowel perforation, which results in the need for admission to hospital and intravenous antibiotics to prevent or treat peritonitis (infection). Occasionally people die from it. In contrast, the faecal blood test for bowel cancer is totally safe and very cheap. It cannot detect cancer as early as a colonoscopy, but if done yearly it detects it early enough and reliably enough to be considered a very worthwhile test.

Therefore, colonoscopy should be reserved for people with higher risk factors (like a family history of bowel cancer) or a ‘positive’ faecal blood test. The higher risk of the procedure is outweighed by the benefit of greater accuracy in these ‘at risk’ cases.

Asprin: a quintessential risk versus benefit debate

While not a screening issue, the risk versus benefit of aspirin use as a preventative measure against heart disease and stroke has been discussed for decades. It is certainly effective, but when someone takes aspirin on a regular basis there is a risk of bleeding from the stomach and in a few cases this can be fatal. The risk of bleeding from aspirin is fairly similar for all people—unless the person also takes other medicines that further increase this risk.

However, the risk of a heart attack increases with age and with other risk factors (such as diabetes, high blood pressure or previous heart disease).

At some stage the benefit of aspirin therapy in terms of reduced risk of a coronary event or a stroke outweighs the risk of aspirin from stomach bleeding. It is now generally agreed that this is at about age fifty for most apparently healthy people.

The risk side of aspirin therapy has been reduced in recent years by a ‘coated’ form that allows the aspirin to pass through the stomach without causing harm. The coating may also increase the benefit side, with more gradual absorption in the digestive tract.

When we are dealing with people who were previously well and happy and who now have a serious health problem as a result of the screening aimed at prevention, we need to consider whether it was all worth it. In some settings (for example, a doctor with lower technical skill checking patients at the margin of the at-risk age), it might be possible that more people die from the screening procedure than from the disease that was the target of the screening in the first place.

Very often it is not the initial screening risk that needs to be considered here. Most initial screening tests are designed to be relatively harmless, cheap, easy to use, and indicative only (as opposed to expensive, more risky and definitive). With the more ‘indicative’ tests, positive results often come back for people who don’t actually have the disease. These results are called ‘false positives’. A cascade of more definitive tests is then often done if the initial test comes back positive. These additional tests often have significantly greater risks than the initial screening test, and need to be factored in to the balance.

Consider this: you are ‘treating’ a whole population, the majority of whom have no disease. You might save five lives per year per 100 000 screened, but four might die from the initial screening processes and the follow-up tests. Allowing for the monetary cost, which was taken from other health programs and could possibly have saved other lives, would you say that this hypothetical screening test is worthwhile?

Unless screening has been shown to save lives in large research projects that are well designed and transparent, they should not be adopted. In other words, when considering the whole population, some screening tests are not worth doing, because the benefits do not outweigh the harm done in the actual testing procedure.

Immunisation

The cost–benefit ratio again needs to be considered with immunisation. Modern vaccines are extremely safe and serious adverse effects are rare, so cost considerations are generally financial, not physical harm.

Recommendations regarding adult immunisation (e.g. influenza, pneumococcal vaccine and vaccines for overseas travel) are largely based on assessment of benefit: what is the chance of catching a nasty and costly disease? This is weighed up against the financial cost of the vaccination.

In some instances, health services pay for the vaccines and this enables more people to be vaccinated, especially if they belong to high-risk groups. If vaccines are not subsidised this is generally because public health authorities have come to the conclusion that the financial benefit is not worth the cost, or there is not enough information about side effects or the protective effect of the vaccine to make a decision. This doesn’t mean that the individual cannot have the vaccine; it’s just that they need to wear the financial cost after assessing the balance of cost versus benefit for themselves as individuals.

Flu vaccine is a good example. It’s free for some people at high risk of severe complications if they catch influenza. However, people at low risk of serious complications may choose to pay for a vaccination because the cost is outweighed by possible loss of earnings, or they have a low discomfort threshold and don’t want to get sick.

At this point you might well ask: ‘If the adverse effects from screening tests and immunisation are rare, isn’t the balance in favour of prevention? These conditions are very common and some of them are deadly. Just look at the health statistics: there seems to be a cancer epidemic at the moment. Surely screening is worth it?’

For recommended immunisations, with the evidence available, the balance is clearly in favour of these preventative health services. For many screening checks, the evidence is less clear. This book takes a detailed look at each screening test as a separate topic. It explains both the benefits and potential problems of the test and it details the recommendations given by various authorities.

References

National Health and Medical Research Council, http://www.health.gov.au/nhmrc/

Canadian Taskforce on Preventive Health Care, http://www.ctfphc.org/

US Preventive Services Task Force, Guide to Clinical Preventive Services, 2nd edn, http://odphp.osophs.dhhs.gov/pubs/guidecps/

---

Defining Normal and Abnormal

A health screening check is a measurement of something. A measurement that is considered ‘normal’ today may be considered ‘abnormal’ tomorrow (or vice versa). This is because all people are different, and for any type of test it is difficult to find what is the ‘normal’ range that indicates good health. And so, as our understanding improves, opinions on what is normal can change.

The ‘normal’ or ‘Gaussian’ distribution curve

When researching aspects of the natural world, scientists have found that many experiment or test results are grouped around an average (which they call the ‘mean’). The number of tests getting a certain result drops sharply for those results that are away from the average, both above and below.

A line graph of the number of times each possible result occurs is often a bell-shaped curve, with the high middle as the mean, and the bottom of the curve on the left and right indicating the rare results that are unusually low or high. For an incredibly diverse variety of scientific experiments and chance outcomes, these symmetrical bell-shaped results distribution curves are so similar that they have similar mathematical properties. Such distribution curves are called ‘normal’ or ‘Gaussian’ curves, and we know, among other things, that they often provide a good description of the characteristics of biological populations.

The deviation of results away from the average

For any set of test results, it can be useful to have a calculated number that represents the extent to which the results are spread away from the average (or ‘mean’). The best one to use is the standard deviation, which is a calculation based on the difference from the average of each test result.

We won’t get too detailed here, but when the statistical concept of the standard deviation is applied to Gaussian curves, one of their special common mathematical properties shows up. If we take two standard deviations to both the right and the left of the centre mean, what is left at the outer end on both sides of the bell-shaped curve is 2.5% of the results (5% in total).

What is normal?

In past years, a common way to define normal was to assume that test results conformed to a Gaussian distribution curve and use the mean plus and minus two standard deviations. These upper and lower cut-off points established where normality ended, and 5% should be left as ‘abnormal’. This is based on the notion that the Gaussian distribution represents an expected range of ‘normality’ for ‘well’ people, and only the extremes should be considered abnormal.

But what if test result data does not conform to a Gaussian distribution? This dilemma could be overcome by just using percentiles and saying that the 5% of results furthest from the average would be called ‘abnormal’. This approach assumes that all diseases have the same frequency in the community, since 5% of all test results are called abnormal. But that is silly.

This approach also creates the strange statistical outcome that almost every healthy person can be proved to be ‘abnormal’ if enough different tests of organs and functions are made.

We’re all sick (let’s do lots of different tests on someone).

This is what happens when we use the above notion that the 5% of results furthest from the average (above or below) are ‘abnormal’:

Test 1: 95% or 0.95 chance of being OK.

Then test 2: 95% of 0.95 (0.95 × 0.95) = 0.9 chance of still being OK.

Then test 3: 95% of 95 × 0.95 = 0.86 chance of still being OK.

By test 20, the chance of still being OK is 0.95 to the power of 20, which is about 1 in 3. With 100 tests, there is only a 6 in 1000 chance of still being called ‘normal’.

The ‘risk factor’ definition of normal–is it better?

An alternative approach is the ‘risk factor’ approach. A test result such as blood pressure is not checked to see if it is in the ‘worst 5%’. Instead, we look at tables based on research studies to see if the result carries an increased risk of illness or death. Unfortunately there is rarely a ‘cut-off’ point above which risk dramatically increases. Usually, the risk increases steadily as the test values deviate from the average, and we have to somewhat arbitrarily choose a cut-off point where ‘abnormal’ begins. Having ‘guessed’ at a cut-off point, and chosen a low one for safety, can we be sure that improving just this one of maybe several risk factors for an illness will improve the person’s chances of longer good health? Improving this risk factor may require an expensive drug and have little effect.

More refined definitions of normal

A diagnostically based decision as to whether a test result is normal or abnormal is more useful. The diagnostic definition of normal applies when there are formally set limits for the normal range of test results, and beyond those limits the target disorder is considered, with a known probability, to be present.

A further step can be made to a therapeutic definition of what is a normal test result. Under this definition, a result is considered abnormal when there is a treatment available that we know from good evidence does more good than harm. The therapeutic definition of abnormal high blood pressure has been steadily falling over recent decades as improved treatments help people long before they reach the extreme end of the scale.

So what is normal?

Patients need to understand that, when faced with test results that are not ‘average’, deciding whether or not the results are ‘normal’ for them can be open to interpretation.

Patient A has a test for a disease. The result is on the 90th percentile, so it could be called in the ‘normal’ range for ‘well’ people based on the expected Gaussian distribution of results. But it indicates increased risk of the disease, so it is possible to call it ‘abnormal’. There are no clear set limits beyond which the disease is said to be present, so the result in a diagnostic sense is ‘normal’. However, we can run with the ‘abnormal’ interpretation because there is a proven therapy for people with this particular test result that greatly reduces the chances of developing the disease.

References

Sackett D, Haynes R, Guyatt G and Tugwell P, Clinical Epidemiology: A Basic Science for Clinical Medicine, 2nd edn, Little, Brown and Company, Boston, 1991.

---

Family History

If everyone were screened comprehensively for everything, using the most sophisticated methods that leave nothing to chance, the capacity and finances of our health system would be overwhelmed. Many individuals would have some equivocal results, be subjected to many more follow-up tests, and suffer all the inconvenience and risk that this entails.

Screening programs for the average person aim to be both affordable and reasonably effective. For some diseases, however, special testing is reserved for ‘at risk’ people. This special testing may mean testing at an earlier age, or more often, or maybe using a more sophisticated method. Often, the main factor that makes someone ‘at risk’ is a family history of the disease.

While it is true that unhealthy behaviour can be passed on within a family (a family history of heart disease may be due to eating lots of saturated fats and heavy smoking), ‘family history’ in a medical context refers to the possibility of illness caused by genetic material inherited from parents. Some parents, while in fact carrying ‘high risk’ genes, can be lucky and not get the associated disease, so that their child may have no inkling of a potential problem. It is therefore wise to also take note of the family history of other close blood relatives, where the disease may have shown up.

Before looking at the theory behind genetic inheritance in the next section, let’s ask some often-asked questions about family history.

Why does my ‘family history’ just increase the risk, rather than making it a ‘sure thing’ that I will get the disease one day?

Genetic inheritance is like a lottery: your parents may have both bad and good genes for a disease. You may inherit only good ones, or a mixture (which is often the same as only getting good ones), or only the bad ones. Until the disease shows up, we usually don’t know if we scored the bad ones. The chance of getting bad ones depends on the number of relatives with the condition. Your doctor may ask about close first-degree (1°) relatives: your parents, siblings or children. The doctor may then ask about second-degree (2°) relatives who are one step removed: grandparents, aunts, uncles, nieces and nephews.

How is the noting of a family history used? Give me a practical example.

Example: Bowel cancer

Family history is the method used to put people into three risk groups: average, moderate and potentially high risk.

Group 1–Average risk or slightly above average risk: 98% of the population

With no family history of bowel cancer, at age 50, the risk of bowel cancer in the next 5 years is 1 in 300 and the risk in the next 20 years is 1 in 30.

People in this group may also have a limited family history: one 1° or 2° relative with bowel cancer at over 55 years of age; or two 1° or 2° relatives with bowel cancer at age 55+ but on different sides of the family.

With limited family history, at age 50, the risk of bowel cancer in the next 5 years is 1 in 150 and the risk in the next 20 years is 1 in 15.

Group 2–Moderate risk: 1 to 2% of the population

People in this group have one 1° relative with bowel cancer before age 55 (and no other risk factors), or two 1° or 2° relatives with bowel cancer on the same side of the family diagnosed at any age.

For group 2, at age 50, the risk of bowel cancer in the next 5 years is between 1 in 100 and 1 in 50, and the risk in the next 20 years is between 1 in 10 and 1 in 5.

Group 3–Potentially high risk: Much less than 1% of the population

These people have three or more 1° or 2° relatives on the same side of the family with bowel cancer; OR two or more 1° or 2° relatives on the same side of the family with bowel cancer that has an additional risk factor (before age 50 or multiple cancers); OR one 1° or 2° relative with FAP (very early growth of multiple polyps); OR any family member with the high-risk ‘bad’ version of the APC or MMR gene.

Group 3 people have a lifetime risk for bowel cancer of up to 1 in 2, or even greater if the high-risk genes are identified by testing.

What is the practical use of creating risk groups?

Continuing with the bowel cancer example, each group is screened differently because the risk established with the help of family history is different. For group 1 people, yearly faecal blood tests from age fifty are the standard recommendation. Group 2 people would, from age fifty, have a five-yearly colonoscopy in addition to the yearly faecal blood tests. Group 3 people may have more frequent colonoscopy, and possibly a genetic test to establish the risk more accurately. They may also start the screening process from an age younger than fifty years.

If ‘family history’ means ‘genetic inheritance’ why don’t we use the new genetic testing to establish the risk of future illness, and not bother with family history?

Establishing the level of disease risk would be more accurate if we could substitute genetic testing for family history. Let’s look now at why the application of genetic testing is very limited.

Before genetic testing was possible, family history was often the only way to know if someone was at increased risk of an illness. A lot of good research was done to find evidence of the importance of family history for individual diseases. As a result, family history is a very effective and virtually no-cost way of establishing risk when looking at the whole population. And, despite the emergence of genetic testing, family history medical research continues as strongly as ever because for the foreseeable future it will not be replaced by extensive genetic testing.

There are also many instances in which useful genetic testing may not be possible. Many genes can be involved in diseases—this applies to many cancers and coronary vessel disease, for example. It is true that one gene may be found to be more important than some others, but testing for one gene only when many are involved may provide very limited help with risk assessment. Family history may be much more accurate!

Finally, genetic testing is expensive. For the individual, it’s true that it may replace the idea of probability of gene inheritance with certainty of a test. In the introduction we referred to sophisticated tests being affordable to the health system for ‘high risk’ people only. Genetic testing is an example of a sophisticated test. It’s not for general risk assessment, but it provides more accurate information when a ‘high risk’ situation is indicated.

If you inherit a ‘bad’ gene–whether you know it through genetic testing or not–are you certain to get the disease in later life?

Some diseases are clearly linked to mutation in one specific gene. If you inherit the mutation, you will most likely get the illness.

Example: Genetic Haemochromatosis (GH)–‘excess iron’ disease

If you have the mutation you are likely to get this disease. High blood iron levels and/ or a family history indicate high risk. GH can then be confirmed with a genetic test in ‘high risk’ people. When family history indicates a very high risk, genetic testing can establish at a young age whether you can forget it, or whether you have the disease and must manage it. Management is easy—you get rid of iron by donating blood.

However, most diseases are due to many factors. Having a ‘bad’ gene set (called a mutation of the normal gene) does not mean you are certain to get the illness. Other genes that you don’t have may be involved, and lifestyle factors may play a big part.

What should I do?

Try to make a record of the serious illnesses that have affected your extended family. This can be a challenge when people are interstate or overseas and contact is limited. When you go for a check-up for the various conditions we describe in this book, mention the relevant family history. More frequent or more sophisticated testing than is normally the case may be sensible if family history indicates higher risk. Pass the family history profile on to your children—they will need it, too, when they reach adulthood.

Reference

The Cancer Council Victoria, Best Advice on Familial Aspects of Bowel Cancer: A Guide for General Practitioners, 1998.

---

Genetic Inheritance

Why do some people inherit a risk of disease from their parents while others do not? It’s because we receive only 50% of our genetic material from each parent. If a parent has a ‘bad’ gene, it may or may not be in the 50% of genes we get from that parent. And even if we get a ‘bad’ gene, it may not cause much trouble unless we get a matching ‘bad’ gene from the other parent. Let’s look at how this works in a little detail.

The basic words and concepts of genetics

Chromosomes, DNA, nucleotides and genes Our genetic information is held in all our cells in 23 chromosomes. The chromosomes consist of DNA spirals. DNA consists of many sequences of 4 different nucleotides. One nucleotide sequence is called a gene.

Proteins

A cell reads genes to create not only the different proteins needed to build our body but also the many other proteins that regulate the operation of our body.

Mutation

Sometimes genes get damaged; this is called a mutation. Most mutations are bad because when the cell reads a faulty gene it makes a faulty protein, and something in our body may not work properly.

Each specific gene occurs as a pair

All of our cells contain two complete sets of genetic information. Each chromosome consists of two nearly identical DNA spirals. One is inherited from our mother, and one from our father. Two sets is good news: if a gene has a mutation, the same gene in the other set may be good, so our cell can still produce the particular protein we need, and with any luck we won’t have a shortage of it.

As in a game of chance, outcomes are described in terms of probability

At fertilisation, we get one of our mother’s two gene sets, and one of our father’s, giving us a double set of our own. If our mother and/or father has a set with a mutation, let’s hope we get their ‘good’ sets and avoid the faulty gene.

Imagine a gene ‘A’ and a faulty version ‘a’. Imagine mother’s gene sets both have good ‘A’ genes, so mother is ‘AA’. Father is also ‘AA’. There’s not an ‘a’ to be seen, so the children must always be ‘AA’. If the mother is ‘Aa’ (has one ‘bad’ gene) and the father is ‘AA’, then the four possible combinations in the children are:

The same applies if the father is Aa and the mother is AA. There is a 1 in 2 chance of a child carrying the faulty gene (the Aa combination), but since such a gene set includes the ‘good’ A gene, they are unlikely to have a problem. Be aware, though, that having one faulty version of a gene can occasionally result in a mild disability, compared with a serious disability if both genes in