Minimal within-day variation of high density lipoprotein cholesterol and apolipoprotein A-I levels in normal subjects.

Blood was drawn from twenty normal hospital employees after a 12-14 hr fast (9:30 AM), and at 4 hr (1:30 PM) and 7 hr (4:30 PM) thereafter while test subjects consumed their habitual diet. Absorptive chylomicronemia was reflected in average triglyceride increases of 30% and 53% at 4 hr and 7 hr, respectively. No significant changes in total (< 1%) and high density lipoprotein (< 0.1%) cholesterol concentrations were observed. Moreover, levels of the major high density lipoprotein apolipoprotein, apoA-I, varied by less than 3%. Blood samples, randomly obtained during standard working hours, appear adequate for quantitation of high density lipoprotein cholesterol and apolipoprotein A-I levels.