CORRELATION BETWEEN THE RATIO OF SERUM LOW-DENSITY-LIPOPROTEIN CHOLESTEROL AND HIGH-DENSITY-LIPOPROTEIN CHOLESTEROL WITH THAT OF SERUM APOLIPOPROTEIN-B AND APOLIPOPROTEIN-A-I

Phosphowolframate/magnesium chloride, a commonly used precipitation me thod for the determination of high-density lipoprotein cholesterol in human serum, yields a supernatant containing almost all of the lipopro teins apo A-I and apo A-II but no lipoprotein apo B. The correlation b etween high-density lipoprotein cholesterol and apo A-I was very high (r = 0.94), as well as that between the precipitation method and ultra centrifugal analysis (r > 0.95, P < 0.001). In contrast, detergent pre cipitation (for the determination of low-density lipoprotein cholester ol in human serum) produced sediments which contained the major propor tion of apo B and only minor amounts of apo A-I and apo A-II. The prec ipitation method for low-density lipoprotein cholesterol showed very g ood agreement with ultracentrifugal analysis (r = 0.99). Yields of 80. 2% were obtained for apo B with both methods. Results obtained using t he precipitation methods showed excellent agreement with those obtaine d using the Friedewald formula (r > 0.99). Results were also very simi lar when hypertriglyceridemic serum samples were briefly centrifuged b efore analysis of cholesterol, high-density lipoprotein cholesterol an d triglyceride values. The present study shows highly significant corr elations between cholesterol/high-density lipoprotein cholesterol or l ow-density lipoprotein cholesterol/high-density lipoprotein cholestero l and apo B/apo A-I ratios (P < 0.001). Apo B and apo A-I levels could be used in addition to low- and high-density lipoprotein cholesterol values when assessing the risk of cardiovascular disease, if the metho ds for determining serum apolipoproteins have been properly standardiz ed.