APOLIPOPROTEIN-B AND APOLIPOPROTEIN-A-I IN RELATION TO SERUM-CHOLESTEROL AND TRIGLYCERIDES IN 43,000 SWEDISH MALES AND FEMALES

Automated methods for the determination of apolipoprotein B and apolipoprotein A-I were developed, tested, and applied in screening programs of large populations to improve information about the composition and degree of hyperlipoproteinemia. Apolipoproteins B and A-I, total cholesterol, and triglyceride levels were measured in 25 659 males and 18 144 females between 20 and 79 years of age, the majority subjectively healthy. The immunoturbidimetric methods used for apolipoproteins B and A-I were shown to be stable over time, and the errors of the methods were below 7%. Apolipoprotein B correlated with total cholesterol (r = 0.86, P < 0.001) for each age decile group and for both sexes (r = 0.82-0.87, P < 0.001). For a subsample comparable to the large population, apolipoprotein B correlated with cholesterol in low density (i.e., the atherogenic particle), r = 0.89, P < 0.001. The mean values for apolipoprotein B increased with age for both sexes, with much higher levels in males than in females under 50 years of age. Apolipoprotein A-I was lower in males than in females in all age-groups. At all cholesterol levels males had higher apolipoprotein B, and at the same triglyceride level, also lower apolipoprotein A-I and hence a higher B/A-I ratio than females. Using apolipoprotein B and A-I (high-density lipoprotein cholesterol) particles and adopting Swedish consensus criteria for the diagnosis of risk of ischemic heart disease, examples are given showing that many individuals, especially females, with high or borderline total serum cholesterol can be excluded from further investigation/treatment for hypercholesterolemia. In the age-group 40-49 years, a total cholesterol value of 6.5 mmol/l was found to correspond to an apolipoprotein B value of 1.39 g/l for males and to 1.32 g/l for females. Whereas 30% of males and 18% of females had total cholesterol values greater than or equal to 6.5 mmol/l, 19.7% of males and 7.5% of females had apolipoprotein B levels above 1.5 g/l (this cut-off point corresponds to a low-density lipoprotein cholesterol value of 5.0 mmol/l). It is suggested that the determination of apolipoprotein B and A-I levels be used to back up screening and facilitate the diagnosis of atherogenic and treatable high serum lipids.