Health: Screening tests don’t guarantee a better outcome

The campaign to encourage more women to have smear tests in response to the death of Jade Goody from cervical cancer is unlikely to benefit their health. While the crusading Sun demands that cervical smear tests be offered to all women over the age of 20, I have already had two teenage virgins in my surgery terrified of facing the same fate as Jade unless they have the test.

Screening tests are a potent symbol of our age of anxiety, where the cult of health promotion feeds on the worries of perfectly healthy people. Everybody – politicians, journalists, doctors, testing entrepreneurs, the public – wants more screening tests. Women want smears and mammograms, men want rectal examinations and prostate-specific antigen tests, and everybody wants to know their blood pressure, their blood sugar and their cholesterol levels.

The popularity of screening arises from the alluring prospect that early diagnosis guarantees a better outcome. Despite its powerful, seemingly commonsense appeal, this notion is based on a number of dubious assumptions.

One is that late diagnosis is a common cause of premature mortality. Like every doctor, I have my stories of patients who turned up late with advanced cancers. But, particularly in recent disease-aware times, their tardy appearance in my surgery is likely to be the result of a personal decision rather than ignorance. No doubt doctors sometimes fail to diagnose cancers early. As a GP, I encounter much bigger problems in delays in investigation and treatment. And, despite improvements, effective treatments for many cancers remain elusive.

Predictive inaccuracy

Another shaky assumption is that screening tests have a high level of predictive accuracy. In fact, all yield some false positives (diagnosing cancer where none exists) and some false negatives (failing to diagnose a cancer where it does exist).

A bigger, though less widely recognised problem, is that screening tests turn up conditions of uncertain significance which may never progress to cancer, but once detected are generally treated as though they would. Such conditions are commonly detected by smears and mammograms, leading to unnecessary treatments with surgery, radiotherapy and chemotherapy.

Take mammography. A recent authoritative review, published in the British Medical Journal, indicated that if 2,000 women are screened regularly for 10 years, one will benefit while 10 healthy women will become cancer patients and undergo unnecessary treatment. Furthermore, about 200 women will experience the psychological stress of a false alarm.

Climate of blame

The current obsession with screening tests fosters a climate of blame and recrimination around the diagnosis of cancer. When people discover they have cancer they often blame themselves for not assiduously examining their breasts (or testicles) – both tests of proven uselessness – or for not attending punctually for screening tests. Family members and friends blame the patient for not going earlier to the doctor for screening tests or other investigations. And everybody blames the doctor for not diagnosing the cancer before anybody knew it existed.

The logical conclusion of the screening mania is that everyone should live in a hospital, preferably in an MRI scanner, so that any disease can be detected at the earliest opportunity.

Others might reflect that, if you develop cancer, you will know soon enough. And in the meantime, you can get on with living your life rather than becoming preoccupied with delaying death.

Michael Fitzpatrick is a GP in Hackney, London. His book, Defeating Autism: A Damaging Delusion, has just been published by Routledge

This article is published in the 9 April issue of Community Care under the heading Jane Goody and the dubious benefits of cancer screening

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