How "representative" are subjects attending a coronary risk factor screening programme?

Coronary risk factors were compared in two groups of subjects aged 25-64 years. One group voluntarily, and at no cost, attended a risk factor screening clinic (n = 3844), while the second group represented a population sample drawn from the metropolitan Sydney electoral roll (n = 1394). Older subjects were over-represented in the screening clinic compared with the electoral roll sample. Hypercholesterolemia was more prevalent in the screening clinic in older females, while hypertension and current cigarette smoking were less prevalent in the screening clinic in older subjects of both sexes. Obesity was less prevalent in the screening clinic in older males. A voluntary screening programme may generate a unique and possibly unreproducible population sample.