August 1990

Day-to-Day Variability of Serum Cholesterol, Triglyceride, and High-Density Lipoprotein Cholesterol Levels

Arch Intern Med. 1990;150(8):1653-1657. doi:10.1001/archinte.1990.00040031653012

The National Cholesterol Education Program has recently published guidelines for the assessment of cardiovascular risk and goals for laboratory accuracy. To test the impact of biologic and analytic variability on the ability of a single lipid measurement to assess risk accurately, lipids were measured on three occasions in 51 volunteers. Notable day-to-day variability of total cholesterol (5%), triglyceride (20%), high-density lipoprotein cholesterol (10%), and calculated low-density lipoprotein cholesterol (8%) levels was found. Analytic variability contributed significantly to total variability of high-density lipoprotein cholesterol levels and calculated low-density lipoprotein cholesterol levels. Confidence intervals constructed around National Cholesterol Education Program cutoff points suggested that classification was reliable from a single measurement if total cholesterol value was below 4.78 (<185 mg/DL), between 5.56 and 5.81 (215 and 225 mg/DL), or above 6.59 mmol/L (>225 mg/dL). Low-density lipoprotein cholesterol value classification from a single measurement was only accurate at below 3.00 (<1166 mg/dL) or above 4.50 mmol/L (>174 mg/dL). This study documents significant day-to-day variability of serum lipids and suggests that patients near the National Cholesterol Education Program cutoff points may require repeated measurements to assign risk accurately.

(Arch Intern Med. 1990;150:1653-1657)