Medical screening

Over the past few weeks, I have been offered massages, gym visits, vitamin supplements, make-up tips and consultations with cosmetic surgeons. All these generous invitations came from PR companies keen to create a media glow for their clients’ products. Since an awful lot of column inches seem to be devoted to genome testing at the moment, I began to wonder if this was the latest thing being dangled under journalists’ noses.

There are numerous reports in the British media of how marvellous and easy it is to undergo genetic screening. You simply give a sample of your DNA (a swipe of your cheek on a swab will do) and hand over your cash (anything from hundreds to thousands of pounds, depending on the company). Voilà, by return of post, you are told your “genetic risk profile”.

Two themes emerge from the articles written by these journalists staring, rapt in wonder, at their own genetic code. First, they see this as a part of the information revolution: at last we are in charge of our destiny; no longer are paternalistic doctors preventing us from discovering what we have the right to know. Second, doctors better get themselves trained up on how to use this information; if they don’t, the service the consumer pays for won’t represent value for money. It’s doctors’ responsibility to help us use this information appropriately.

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I am reporting good news, for a change. The UK Breast Screening Service has said it intends to rip up the leaflet which is currently sent to women with breast screening appointments. A recent paper in the British Medical Journal outlined the kinds of uncertainties and likelihoods the authors thought would have counted as “fair information” to give to women. This seems to have prompted UK Breast Screening to review the content of its leaflet and try to give better information.

I am a GP, and so my perspective on what is “better” will likely take account of the difficulties which I observe breast screening leading to. My wish list starts with wanting the new leaflet to describe screening explicitly as an intervention which one can accept or decline. Breast screening should not be something which is sold, or which one is persuaded or coerced into. Women should be treated as competent adults who have the pros and cons explained to them: it is simply not ethical for breast screening to proceed without proper counsel.

People have written entire books about the problems of screening. I will stick to just two things: “overdiagnosis” of what is sometimes called “pseudodisease”, and limited gain. “Overdiagnosis” relates to the fact that it’s not just full-blown cancers that are detected. Some of the abnormalities seen and biopsies examined can represent situations where the prognosis is uncertain. Some of these are a condition called “ductal carcinoma in situ”. This makes up about 20 per cent of “breast cancer” diagnosed at screening in the UK. While these are commonly treated with surgery and possibly chemotherapy and radiotherapy, only a minority may end up progressing to a life-threatening cancer. Studies done at autopsy imply that 15 to 39 per cent of women die with, rather than from, this type of cancer.

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And lo, the government said, we must woo voters. And they had a great idea: check ups. Let’s not leave them to the private providers. Let’s put them on the NHS. Everybody loves a check up.

The Department of Health sets out its new idea in a policy paper “Putting prevention first – vascular checks: risk assessment and management”. This includes the laudable aim to prevent ‘at least’ 9,500 heart attacks and strokes in a year. It is also estimated that the program could prevent 4,000 people from developing diabetes and ‘detect at least’ 25,000 people ‘earlier’ with diabetes or kidney diseases.

I’m beginning to think that this sounds suspiciously like a screening programme. The publication goes on: the vascular risk assessment programme will enable ‘everyone between 40-74 in the population to have their vascular risk managed appropriately’. Sounds daunting. Millions of people will be need to be assessed, and an enormous amount of healthcare staff time will be diverted. In light of this, one should expect this scheme to have been tested in real world situations with real world benefits in the UK population it is targeted at. One would be interested especially in medium and long term effects. One would also hope that adverse effects and cost efficiency have been examined. Instead, most of the work examining the effects of this scheme has been done through assumptions and modelling scenarios.

Further, because most of the work is intended to be done outside of GP surgeries, medical advice is not always going to be readily available. I cannot be the first doctor to have been faced with an anxious patient concerned that a cholesterol reading performed beyond the surgery has been found to have been marginally, and inconsequentially, higher at a private providers. I would not have wasted resources in needlessly repeating a test, but this is only going to be a small part of the difficulties of this new scheme. Screening tests should be done as part of an evidence-based policy which acknowledges the possibilities of false positives, negatives, and impact of tests on peoples’ lives.

Screening tests are complicated, messy and confusing. Throwing inadequately tested tests at the problem is rarely the solution.

I was talking to a composer a few weeks ago. “This stuff doesn’t really exist except when it’s played,” he said, pointing to his score with heavy despair. “Whereas you’ve got a job where you can actually see that you are doing something good.” He couldn’t understand that my protests to the contrary were genuine: doctors cannot always be sure that they are making a positive difference.

Medical history is stuffed with examples of bad practice – lobotomy for just about anyone with a mental health problem, tonsillectomy for most people with a sore throat, bed rest for everyone with low back pain. I may exaggerate, but only a little. Even now, we don’t seem to appreciate the value of analysing what we are doing.

The US Senate has just passed a bill putting $1.1bn into research aimed at identifying which medical treatments work and which don’t. This sounds like a good idea, but of course not all research is created equal. Regular readers will be aware, for example, of the conflicts surrounding the Department of Health recommendation that all over-65s receive a flu vaccination. Some evidence supports vaccination, some indicates that it does not improve mortality rates. What to believe?

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A very interesting paper just published in the Archives of Internal Medicine. The study followed women before and after the introduction of a breast screening programme in Norway. They were compared to a control group of women who did not take part in the screening programme, but who would have been, had the programme been started in their area. This control group were invited for a one-off screening at the end of the observation time in order to work out how many had invasive breast cancers.

When the two groups were compared, the amount of invasive breast cancers was found to be significantly higher in the group of women who had regular screening. On first glance, this may appear to be a good thing – it seems that screening picked up more invasive breast cancers. But is it? The problem is that the natural history of these “invasive breast cancers” may not be as predictable as we would like to think, in that not all may cause a life-threatening situation. The authors concluded that “it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of 6 years. This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress”.

This is but one paper in a complex field, and I wouldn’t suggest that this research alone should make women decide what to do when the invitation to breast screening comes in. However, there are already uncertanties about how beneficial breast screening is. I think this paper does emphasise that there are still a lot of unknowns when it comes to breast cancer screening. The NHS Behind the Headlines service provides a useful analysis of the news coverage of this story but concludes that “women should continue to attend screening programmes”. I think this is a bit unfair; surely the best position is to invite women to weigh up the pros and cons for themselves, as they become known. But maybe this is also unfair; most people probably don’t have the time to devote to investigating this sort of thing and they should be able to expect disinterested, fair advice from their health professionals. 

Regular readers will know that I have concerns about many tests used in the UK for screening. Screening tests are used when people are well, with no symptoms of disease. The aim of screening is to pick up a disease process at an early, pre-symptomatic stage such that an effective intervention can be used to prevent complications.

Real life is rarely that simple. A while ago I was asked (live on radio) for an example of a perfect screening test. Unfortunately, all I had to offer was a long silence as I tried (and failed) to think of one. Instead screening tests offer a balance of probabilities, and the risks and benefits of interventions which can then be offered are usually more complicated the more one examines them. (I’ve just finished reading Sir Muir Gray and Dr Angela Raffle’s excellent book Screening, Evidence and Practice. Raffle is a public health consultant, and Gray was the Programmes Director of the  UK National Screening Programme from 96-07. The first line of the preface is ‘All screening programmes do harm’.)

I am perturbed. The US Preventive Services Task Force, a government health body, has decided that doctors should stop offering prostate-cancer screening to men over 75.

It has made a definitive statement: “Do not screen for prostate cancer in men age 75 years or older.” But instead of happy relief at this rare outbreak of common sense, there has been outcry.

Men’s health, the accusations go, is being left out in the cold, for dead. Since I wrote a few lines on this subject on my FT blog, I have received a stream of unhappy e-mails from people distressed that they might now not be recommended to have this “life-saving blood test”. One said: “I feel like I’ve been thrown on the scrapheap.”

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Pharmacists were reportedly delighted with a new scheme, just announced, to allow for azithromycin, an antibiotic, to be made available without a doctors’ prescription. This drug is a treatment for the sexually transmitted infection Chlamydia. Since Chlamydia infection can be without symptoms, and since, if it is left untreated over time, it can lead to problems such as inflammation and infertility, the idea has been to try and treat as many infections as possible before they cause problems.

This sounds sensible. But as usual the truth is a bit more complicated. This new prescription-free service is part of the Government’s strategy on dealing with sexual infections, and it hinges on screening for Chlamydia. Crucially, testing for this no longer needs an internal examination and swab to diagnose it. Instead, Chlamydia infection can be identified on a urine sample. This means that a doctor or nurse to do an internal examination isn’t needed, and that a urine sample can be tested. If positive, the infection can be treated with the over-the-counter azithromycin, and without a doctor.

This approach increases the amount of places to get a diagnosis and access to treatment. But the problems are multiple. There is a lot of concern that in offering only testing for Chlamydia, other sexual infections will go undiagnosed. Doctors are frequently reminded that other infections, initially without symptoms, can be sexually transmitted, particularly HIV and Hepatitis B. Indeed, at least some of the problems resulting in these infections not being diagnosed as early as they could be has been because of the (sometimes understandable) reluctance of healthcare professionals to raise the issue of testing for something which carries a stigma. However, earlier diagnosis brings many benefits, and stigma may simply have been perpetuated by medical reluctance.

But the other issue is whether this scheme will result in more diagnoses of Chlamydia. The ‘approved standard testing kit’ costs £25, and the antibiotic to treat a positive result costs £20. Since testing is free, meantime, on the NHS, and the prescription for a positive result available for either cheaper or free, I am not sure that this new innovation will prove the answer for over-stretched services, as claimed. Indeed there is still considerably dubiety about the effectiveness of opportunistic Chlamydia screening in general. Health economists have pointed out that on current evidence, it does not appear to be cost effective.

Prostate cancer screening via use of a PSA (prostatic specific antigen) testing – a biological marker found in blood – is one of the most contentious things around. There is no such contention over seeking diagnosis and treatment for prostate symptoms. It is screening for problems when no symptoms exist that is the issue.

While the logical view may be that ‘catching things early’ is a good thing, the truth is rather different (I am getting deja vu: exactly the same thing applies to breast self-examination). PSA testing is even messier, though, in terms of potential harms. A high PSA result can be a false positive for cancer (instead inflammation or a benignly enlarged prostate can cause high results) or false negative (PSA is not elevated where there is prostate cancer present). Additionally, the surgical treatment for prostate cancer can result in major side effects (impotence and incontinence). The crux is, that for prostate cancers found at screening, there may be no benefit to the man in question in improving mortality, but there still may be harm done in terms of ‘treatment’.

While in the UK prostate cancer screening is not routinely done, in the US there is a culture that says ‘all men must know their own PSA’, despite the lack of evidence for this. However, today the US Preventive Services Task Force has said that “Current evidence is insufficient to assess the balance of benefits and harms of screening for prostate cancer in men younger than age 75 years” and “Do not screen for prostate cancer in men age 75 years or older”. There are trials ongoing which will hopefully give us better information, but in the meantime, the circumspect approach in the UK (where generally more information given about the limitations and potential harms of PSA screening leads to a decrease in the amount of men who end up having it done) looks like it is the right one.

It  seems so sensible to try and find breast cancers early. Yet the truth in medicine is often counterintuitive, and this is one such example.  

The headlines today are about breast self examination – regular exams done by women themselves looking for lumps – being ineffective to reduce deaths from breast cancer. 

Margaret McCartney’s Blog

This blog is no longer updated but it remains open as an archive.

A forum on healthcare policy and professional issues, by Glasgow-based GP and FT Weekend columnist Margaret McCartney.