Diurnal and monthly intra-individual variability of the concentration of lipids, lipoproteins and apoproteins

Abstract

Diurnal and monthly variability of the serum concentration of lipids, lipoproteins and apoproteins were examined in 11 healthy subjects aged 32-63 (mean 46) years. For diurnal measurements, blood samples were drawn at 0800, 1200, 1500,1800, and 2100 hours. The variability over 1 month was assessed from four analyses taken weekly at 0800 hours after at least 8 h fast. The analytical variability expressed as mean coefficient of variation (CV) ranged from 0.95% for cholesterol to 7.6% for apoprotein B. The mean CVs for diurnal biological variability were 2.4% for cholesterol, 3.5% for HDL-cholesterol, 5.1% for LDL-cholesterol, 29.5% for triglycerides, 6.5% for apoprotein A and 6.5% for apoprotein B. The respective biological CVs for monthly variability were 4.2%, 4.1%, 5.2%, 20.7%, 9.4% and 9.7%. A repeated-measures ANOVA revealed a significant increase of triglycerides (p<0.01) and decrease of LDL-cholesterol (p<0.01) during the day. Within 1 month, apoprotein A tended to rise (0.05<p<0.10).

Although the best reproducibility was found for cholesterol, the results obtained indicate that six tests have to be taken before and after intervention by drug or diet to detect a reduction of 10% in an individual with a probability of 0.95.

Key Words:

• apoproteins
• diurnal variability
• healthy subjects
• lipoproteins
• monthly variability