Predictive value of lipoprotein (a) and other serum lipoproteins in the angiographic diagnosis of coronary artery disease. To determine the relation among lipids in predicting coronary artery disease (CAD), 213 patients undergoing diagnostic angiography for suspected CAD were prospectively studied. Twenty-one patients had normal coronary arteries and 192 had CAD in 1 to 3 arteries at arteriography with measurements obtained with digital calipers. Lipoproteins were measured and lipoprotein (a) [Lp(a)] was also assayed in a subset of 98 patients with CAD. Statistical analysis was performed using uni- and multivariate techniques to test the association among age, gender, systemic hypertension, diabetes mellitus, cigarette smoking, family history, total cholesterol, triglycerides, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, very low density lipoprotein cholesterol, apolipoproteins (apo) A-I and apo B, ratio of apo A-I to apo B, and ratio of HDL cholesterol to total cholesterol, to Lp(a) and to CAD. All factors except gender, systemic hypertension, diabetes mellitus and cigarette smoking were univariate predictors of CAD. Multivariate predictors were, in decreasing order of significance, family history, age, HDL/total cholesterol ratio and apo B. When Lp(a) was included, multivariate predictors were age, family history, apo B and Lp(a), in that order. Lipid parameters alone showed that the HDL/total cholesterol ratio and that Lp(a) provide the best predictive tests for the detection of CAD in this referral population and may ultimately become important screening tests for CAD. 