The performance of blood pressure and other cardiovascular risk factors as screening tests for ischaemic heart disease and stroke.

This paper summarises the main evidence and conclusions relating to using blood pressure measurement as a screening test to identify people who will develop ischaemic heart disease (IHD) or stroke, as recently published in a Health Technology Assessment report. While blood pressure is recognised as an important cause of stroke and IHD, and lowering blood pressure can substantially lower the risk of these diseases, the measurement of blood pressure is a poor screening test. It is not good in distinguishing those who will and will not develop these diseases. The poor screening performance is illustrated by the findings that in the largest cohort study, persons in the top 10% of the distribution of systolic blood pressure experienced only 21% of all IHD events and 28% of all strokes at a given age. Using several cardiovascular risk factors in combination does not add materially to the poor screening performance of blood pressure alone. Among persons in a specified age group, the 5% at highest risk experience 17% of all heart disease deaths with risk computation based on blood pressure alone, 22% when based on blood pressure and apolipoprotein B (or LDL cholesterol) in combination, and only 28% using these two, smoking and three other cardiovascular risk factors all in combination. Identifying patients at the time of hospital discharge following myocardial infarction or stroke is the most effective screening test to identify those who will die of cardiovascular disease. In patients with a history of myocardial infarction or stroke the cardiovascular death rate in the absence of treatment is about 5% per year, a risk that persists for at least 15 years. In the absence of treatment, about half of all deaths from heart disease in a population occur after hospital discharge following the first infarct. Among persons with no history of cardiovascular disease, age is a better screening test than the reversible risk factors, and the best policy is to offer treatment to all persons above a specified age such as 55 years.