Abstract
The importance of determining high-density-lipoprotein cholesterol (HDL-C) concentration has been unequivocally confirmed by the results obtained in several prospective studies. At the same time, it is shown that the concentration of HDL-C may largely fluctuate under the influence of many factors. The level of HDL-C is usually evaluated as a predictor of atherosclerotic vascular disease. Hence, in the present study attempts were made to thoroughly examine the reproducibility of the HDL-C level and the factors affecting it.
(1) The HDL-C levels were repeatedly measured in 28 healthy males and 29 healthy females to determine their reproducibility. Of the male subjects, three showed marked increases in HDL-C levels (more than 20mg/dl) accompanied by concomitant increases in apo A-I level, but no factors previously reported could be considered responsible for these changes. It is likely that these subjects might have been undergoing subclinical damage to the intestine or liver at the time of the initial examination followed by natural convalescence. When these particular cases are excluded, the mean variations are 4.9mg/dl for males and 8.1mg/dl for females. These results lead us to conclude that the second value of HDL-C which was determined at least one month later should fall within the experimental error of the first value to estimate the HDL-C level inherent to the individual. When the HDL-C level was measured in patients, the mean variations were much larger than those in healthy subjects.
(2) It is well established that the serum HDL-C level negatively correlates with the serum triglyceride level in cross-sectional studies. In fact, significant negative correlations were found among each of the whole male and female groups we examined, including patients with various diseases and healthy subjects. When these cases were divided into 13 groups according to the underlying diseases, and the correlation between HDL-C and triglyceride levels was examined in each group, no significant negative correlation could be observed except for two groups. In the present study, serum HDL-C and triglyceride levels were reexamined in 28 healthy males and 29 healthy females after some intervals, which averaged 8 months for males and 12 months for females. Hence, whether or not the difference in the HDL-C level correlated with the difference in triglyceride level between the first and second examinations was studied. No significant negative correlation was found in this longitudinal study.
