Jane McCredie: A testing review

WHEN a Cochrane Review last week found regular health checks in asymptomatic people offered no benefits in mortality or morbidity, it prompted news stories around the world.

“Annual health checks do not reduce mortality” was the headline in the BMJ or, as Fox News put it: “Yearly physicals deemed ‘meaningless’ for healthy people”.

The authors of the review concluded that their results “[did] not support the use of general health checks aimed at a general population outside the context of randomised trials”.

Public health initiatives to systematically offer general health checks should be resisted, they wrote, based on their review of 14 randomised trials that included more than 180 000 participants with a median follow-up time of 9 years.

So does this mean GPs should stop testing blood pressure, cholesterol and HbA1c levels in asymptomatic patients?

Well, not so fast.

The authors did point out that GPs identifying and treating risk factors and diseases when patients attend, often for other reasons, might be partly responsible for the seeming lack of efficacy of formalised health checks.

And they also noted that most of the included trials were old, acknowledging this made the result less applicable to today’s setting given more recent changes in the treatment of conditions and risk factors.

But what they failed to spell out — and it certainly wasn’t in the press release — was that nine of the 14 included trials dated from the 1960s and 1970s.

The largest trial, accounting for more than a quarter of total participants, was a WHO study on screening for coronary risk factors in European male factory workers conducted in 1971.

Is a study conducted 40 years ago, before the advent of statins and angiotensin-converting enzyme (ACE)-inhibitors, really a reliable guide to whether we should be testing cholesterol and blood pressure today?

The Cochrane authors rightly pointed out in the body of their report that the introduction of new treatments had brought both potential benefits and risks.

“Thresholds for treating cardiovascular risk factors and diabetes are lower today than at the time most of the included trials were conducted”, they wrote.

“This has led to increased prescription of preventive drugs with demonstrated efficacy … However, the balance between benefits and harms may be unfavourable when the absolute risks are low, such as in a screened population, or when used in more heterogeneous populations with more co-morbidities.”

“Thus, we cannot know whether results would be better today.”

And that, buried on page 25, is the real message of this review: not that contemporary health checks are useless, but that we have no idea whether they do more good than harm because we simply don’t have the data.

The principles of evidence-based medicine need to apply to screening just as they do to active treatment, given the risks of false-positive results, such as unnecessary treatment, psychological distress and financial cost to individual patients and to the health system.

Such issues have been widely canvassed when it comes to some forms of screening — prostate cancer comes to mind — but are less likely to come up when we’re talking about routine monitoring of blood pressure.

Those kinds of preventive health tests seem, intuitively, to be a good thing, but intuition really isn’t enough.

We need quality data from long-term studies reporting not on surrogate outcomes such as cholesterol levels, but on real clinical ones like mortality and myocardial infarction.

This Cochrane Review doesn’t give us that, but perhaps it points the way.

Jane McCredie is a Sydney-based science and medicine writer.

Posted 22 October 2012