Precision of blood cholesterol measurement and high blood cholesterol case-finding and treatment.

Imprecise blood cholesterol measurement can be expected to adversely affect large scale efforts to detect and treat high blood cholesterol. Using protocols specified by the National Cholesterol Education Program (NCEP), we used computer simulation techniques to quantify the effects of blood cholesterol measurement variability on misclassification rates, costs, effectiveness, and cost-effectiveness of high blood cholesterol case-finding and treatment. At the time of initial case-finding, increased measurement variability was associated with a moderate decrease in the proportions assigned to a treatment state and in the positive predictive value of such an assignment. After 10 years of continual case-finding and treatment, measurement variability dramatically affected proportions assigned to drug treatment and diminished the percent on drugs with blood cholesterol levels truly above NCEP cutpoints. Extreme variability in blood cholesterol measurement increased per capita costs by 14-18% and diminished cost-effectiveness by at least 11-12%. The adverse effects of measurement variability on cost-effectiveness were much more pronounced if adjustments to life-expectancy were made to recognize the lower quality of life associated with drug treatment. Misclassification rates can be decreased and cost-effectiveness improved by performing repeated measurements of blood cholesterol before increasing intensity of treatment. Improvement in the precision of measurement are especially beneficial for low-risk individuals.