Invasive versus noninvasive studies of risk factors and atherosclerosis.

Associations of risk factors with atherosclerosis may he assessed by either invasive methods for measuring the arterial disease, such as angiography, or noninvasive methods; these methods differ in their potential for bias. Biases associated with coronary angiography may he difficult to control in statistical analysis, either because they are unrecognized or because they are amenable to neither stratification nor multivariate analysis. Problems in control selection include the likelihood that angiography controls overrepresent related ischemic or noncoronary cardiac conditions with their own risk factor associations