Variability and classification accuracy of serial high-sensitivity C-reactive protein measurements in healthy adults

Background: Increased concentrations of high-sensitivity C-reactive protein (hs-CRP), a marker of systemic inflammation, are associated with increased risk for coronary heart disease. Because of its relationship to inflammati on, hs-CRP has considerable biologic variation. This study was carried out to characterize CRP variation and to compare it to another risk factor, tot al serum cholesterol. Methods: One hundred thirteen individuals were scheduled to have five measu rements each of hs-CRP and total cholesterol carried out at quarterly inter vals over a 1-year period. Variations of hs-CRP and total cholesterol were characterized, and classification accuracy was described and compared for b oth. Results: The relative variation was comparable for hs-CRP and total cholest erol. When classified by quartile, 63% of first and second hs-CRP measureme nts were in agreement; for total cholesterol it was 60%. Ninety percent of hs-CRP measurements were within one quartile of each other. This relationsh ip was not altered by the use of log-transformed hs-CRP data. Conclusion: hs-CRP has a degree of measurement stability that is similar to that of total cholesterol. (C) 2001 American Association for Clinical Chem istry.