The analytical variation and mean difference of serum lipid values in duplicate samples subjected to different times of storage

Two successively drawn blood samples were collected from 100 randomly selected persons and analysed for total-cholesterol, HDL-cholesterol and triglycerides in serum. One sample from each person was sent directly to the laboratory, while the other was kept refrigerated for 7 days before it was sent. Coefficients of variation for the laboratory variation were 2.0%, 12.4% and 4.7% for total-cholesterol, HDL-cholesterol and triglycerides, respectively. There were no significant differences between the first and second drawn sample for either of the variables. We found small, but significant decreases (P less than 0.001) from directly sent to stored samples for total-cholesterol and triglycerides. The correlations between the two samples were 0.99, 0.76 and 0.99 for total-cholesterol, HDL-cholesterol and triglycerides.