Doctors are warning the public that unregulated elective screening tests – such as whole body CT scans or early mammograms – could cause patients far more harm than good.
They say private sector screening tests, which can be heavily marketed and not always to the people most at risk of a disease, are becoming more popular in the UK. In 2004 alone, private tests including whole-body computerised tomography (CT) scans, ECGs (electrocardiograms), mammograms in young women and PSA tests for prostate cancer, raked in £65 million.
The medical evidence for the benefits versus harm of the privately-funded screening is “often quite sketchy”, says Charles George, chair of the British Medical Association’s board of science, which published the report on screening on Tuesday.
The report says unregulated screening is often for profit – unlike national screening programmes – and may not have good quality control. Information and support for patients may also be lacking, the document claims.
The report stresses that “screening is a whole system, not just a test”. In the UK there are several nationally run screening programmes available for free via the country’s National Health Service. These include breast cancer screening for all women aged 50 to 64, and the newly announced national bowel cancer screening programme, scheduled to start in April 2006.
“Where tests are going to be of advantage to people they are available as national screening programmes, “ asserts Vivienne Nathanson, the BMA’s head of science and ethics. “They are carefully structured to make sure they maximise benefits and minimise the harms.”
Boosting cancer risks
Unregulated screening can expose people to significant harms, warn the doctors. For example, a CT scan exposes patients to a dose of ionising radiation 100 times the dose used in a chest X-ray. “We have very severe concerns about people opting for this very significant dose,” says Nathanson. “Most of us wouldn’t go for this if we were well.”
Steven Laitner, a consultant in public health medicine and a family doctor, points out that having a whole-body CT scan increases the risk of a person subsequently developing a fatal cancer to 1 in 2000. “Because the whole body CT scan is looking throughout the body you are likely to find some abnormality. However, to prove that a very small lung nodule is not a cancer people need to have an invasive test,” he says.
“And some very small cancers go away of their own accord,” he adds. Therefore, someone screened in this way may then go on to have invasive surgery where they may never have developed lethal cancer in their lifetime anyway. Such arguments have been applied to prostate cancer in particular.
And positive results from screening – whether true or false, or from a regulated programme or an elective test – can lead to significant psychological trauma, the report warns.