RELIABILITY OF C-REACTIVE PROTEIN MEASUREMENT IN GENERAL-PRACTICE IN THE NETHERLANDS

The aim of this study was to compare the reliability of the whole bloo d Nyco Card C-reactive protein measurement (CRP) with the erythrocyte sedimentation rate (ESR) in four general practice centres (GPCs) in Th e Netherlands with 443 patients indicated for ESR. During 4 successive months in 1992 NycoCard CRP was measured in capillary (whole) blood a t the GPC. A venous blood sample was then transported to the local hos pital laboratory in order to determine CRP turbidimetrically in plasma . Westergren's ESR was measured at the GPC and at the laboratory. The dichotomized CRP values measured at the GPCs corresponded with the lab oratory values in 88% of the cases. Kappa was 65% (p < 0.00001). Using a 20 mm cut-off point, ESR values measured at the GPCs and the labora tory corresponded in 96% of cases (Kappa = 90%, p < 0.00001). Interpra ctice variabilities and learning effects did not influence the results . 'False normal' rates for CRP and ESR were 8% and 1%; 'false elevated ' rates were 28% and 12% respectively. The reliability of the NycoCard CRP measurement in whole blood disappointed. In particular the 'false elevated' rate is unacceptably high for daily general practice. The b ackground of the poor reliability remains unclear.