Physiological and analytical variation in cholesterol and triglycerides

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Abstract
Plasma cholesterol and triglyceride levels were determined, on each of two AutoAnalyzer systems in 11 healthy subjects, weekly over a 10‐week and monthly over a 12‐month period. Analytical variation was 1–2% for cholesterol and 2–5% for triglyceride. Cholesterol and triglyceride values on frozen quality control serum pools were not indicative of absolute values on fresh plasma. Even though the two AutoAnalyzer systems averaged within 1–2 mg/dl for triglyceride and cholesterol on the serum quality control pools during the 12‐month period, the two systems differed by 7–8 mg/dl on fresh or frozen plasma samples. The coefficient of physiological variation on the 10 weekly samples averaged 5% (range 3–10%) for plasma cholesterol and 18% (range 9–27%) for plasma triglyceride. Analysis of the monthly samples suggested significant (P<0.05) seasonal trends: cholesterol was highest in the winter months and lowest in October, whereas triglyceride was highest in January and February and lowest in May and December. We conclude that intra‐individual variation can be an important source of error in attempting to make a genetic diagnosis of hyperlipidemia and/or in evaluating hypolipidemic regimens in a given subject.