URINARY APO(A) DISCRIMINATES CORONARY-ARTERY DISEASE PATIENTS FROM CONTROLS

Increased plasma lipoprotein (a) (Lp(a)) levels are associated with pr emature cardiovascular diseases and stroke. Since Lp(a) immune reactiv ity is found in urine we compared urinary apolipoprotein (a) (apo(a)) with plasma Lp(a) levels in 116 patients suffering from angiographical ly proven coronary artery diseases with that of 109 controls, Urinary apo(a) investigated by immune blotting, revealed a distinct apo(a) fra gmentation pattern with molecular weights between 50 and 160 kDa. Apol ipoprotein B however was not secreted into urine. Lp(a) and apo(a) wer e measured by a fluorescence immune assay. Within single individuals, urinary apo(a) levels correlated significantly with creatinine (Rho, 0 .98; P < 0.0005). Medians and 25/75 percentiles of urinary apo(a) in c oronary artery disease (CAD) patients were 5.70, 3.25 and 10.35 mu g/d l and in controls 2.64, 1.43 and 3.50 mu g/dl respectively. At cut-off levels of 30 mg/dl for plasma Lp(a) and 10 mu g/dl of urinary apo(a) respectively, both paramenters showed comparable sensitivities (33.8% vs. 26.7%), yet the specificity (76.1% vs. 91.7%) and the positive pre dictive value (60.0% vs. 76.4%) of urinary apo(a) were much higher. In receiver-operating characteristic plots, urinary apo(a) was much more sensitive at high specificities i.e. greater than 60% as compared to Lp(a). Urinary secretion of apo(a) fragments normalized to creatinine is stable in a given individual and significantly associated with coro nary artery disease. (C) 1997 Elsevier Science Ireland Ltd.