Testing for high blood pressure can save lives – but experts say that unnecessary tests, such as whole body scans, may just find problems that probably don’t need treatment. So what should you be tested for?

Most health checks are designed to look for risk factors or early signs of diseases – the two most common being heart disease or cancer. A quarter of premature deaths are caused by cardiovascular disease (heart attacks and strokes) and an estimated 50-80% of them are preventable. So any checks that could help early detection are surely a good thing.

Dr Matt Kearney, a GP and the national clinical director for cardiovascular disease prevention, welcomes the growing trend for people to take control of their own health, but he says that the challenge is judging which tests are likely to do more harm than good. “We should democratise health information so everyone has access to it; doctors need to welcome people knowing more and help them to navigate options. Screening is attractive to individuals who look for reassurance that they’re healthy.”

The NHS offers a health check every five years to everyone aged between 40 and 74 to pick up early signs of stroke risk, diabetes, dementia, and heart and kidney disease. Kearney says there is a clear rationale for these checkups, despite criticisms that they pander to the worried well, are a waste of resources and lack clear evidence of effectiveness. “We don’t have evidence of long-term benefits yet,” he says, “although initial reports are encouraging. However, the tests and interventions in the NHS checkup are all evidence-based. The alternative would be to do nothing – but we have an epidemic of preventable ill health, such as diabetes, so we need to do something now.”

The scale of undetected conditions such as high blood pressure is enormous. The British Heart Foundation estimates that seven million UK citizens have undiagnosed high blood pressure, increasing the risk of heart disease or a stroke. Kearney says that, of the 1.5 million adults in England who have taken up the NHS health check, one in 27 were found to have high blood pressure of which they were previously unaware. Of course, the next step is to make sure that, once detected, it is treated; 40% of people with diagnosed high blood pressure don’t achieve optimal targets. But better detection and treatment could prevent an estimated 14,500 strokes and 9,710 heart attacks in England over the next three years.

The risk factors that commonly available checks are trying to identify are high blood pressure, poor diet, high cholesterol, obesity, smoking, alcohol and drugs, poor kidney function, lack of exercise and air pollution. To help achieve this, and improve uptake, Kearney wants the standard NHS health check to be available in public places, such as leisure and shopping centres and for pharmacists and a range of healthcare professionals to be on hand if tests flag up problems. Then there are national screening programmes for early detection of cervical, breast and bowel cancer, as well as aortic aneurysms.

But what if you are too young or too old for the NHS check – or have worries, but have been checked recently? And what about rarer conditions, such as thyroid cancer or brain tumours? Should people who worry about these go for a full MOT, complete with whole body scan, blood tests, lung function and heart tests? Then, too, there are the “gender-specific tests” – ovaries and breasts for women, testes and prostate for men?

In fact, men are often offered a blood test to detect prostate problems as part of a health check and are told that it can be an indicator of cancer. But Prof Timothy Wilt of the University of Minnesota’s medical school says that he wouldn’t recommend it: “At best, the benefits are small and the risks are considerable.” Two big trials have shown no reduction in deaths from prostate cancer picked up at screening.

The idea of a whole body scan is attractive; Oprah Winfrey kickstarted a rush 17 years ago when she had one. But Prof Gilbert Welch of the Dartmouth Institute in the US is wary. In a study of more than 1,000 healthy middle-aged adults, whole body scans uncovered an average of 2.8 abnormalities each. More than a third of them needed a follow-up. “Screening scans can trigger a cascade of events that ends in surgery,” says Welch. “People need to be very aware of what they’re getting into. The human body is full of abnormalities, modern imaging is very sensitive and we don’t know how to interpret everything we see.” A study by Welch has found that regions of the US with higher rates of routine – often unnecessary – scanning have higher rates of nephrectomy (surgical removal of a kidney.) He thinks the two are connected.

“Whole body scanning can unearth a Pandora’s box of ‘incidentalomas’ – spots on your liver, lungs, adrenal gland, thyroid gland, ovary, pancreas and kidney. We doctors aren’t sure what they mean, so we tend to investigate them – an investigation that typically involves getting tissue, which requires needles and other surgical procedures. Whether anyone is helped by the process is hard to know, but it is easy to see how they can be harmed: unnecessary anxiety, unneeded surgical interventions and their attendant complications, including, rarely, death,” says Welch.

But what about stories of perfectly well people who go for a brain scan, find they have an aneurysm (bulging, fragile blood vessel), have an operation to clip it and avert a possible stroke? Surely that’s something you would fork out for. But Dr Margaret McCartney, a GP who presented a BBC radio documentary on screening, points out that increasing diagnosis may not result in better outcomes. The prime example is a mass screening programme for thyroid cancer in South Korea that detected 15 times more cases than previous tests, with no net improvement in death rates from the disease to date. If everyone were scanned for aneurysms, around 2% of people would be found to have one – but, since most would never cause problems, intervention might well do more harm than good.

McCartney says: “If a screening test is cost-effective, the NHS is doing it. We don’t have evidence for additional tests at the moment.” She thinks that people don’t get adequate information about the potential hazards of some commercially available tests; the stress and anxiety, false positives (when a test suggests an abnormality that turns out to be nothing) and false negatives (when a test is reported as OK, but isn’t, giving a false sense of security). The false positives get handed back to the NHS to deal with, which is “fundamentally unfair, immoral and unethical”.

Kearney, though, says people should make their own choices about what they want to check out. And anyone with new, unexplained or worrying symptoms, a family history of a particular condition or a particular health concern should always see a healthcare professional, whether they have had a health check or not. The expert consensus seems to be: go ahead with commercial checks if you want to – but buyer beware, and very aware.