High-sensitivity C-reactive protein methods examined.

Because C-reactive protein (CRP) has prognostic value in patients with acute coronary syndromes and in apparently healthy people (1), various high-sensitivity CRP (hs-CRP) methods have been introduced (2)(3). For the clinical laboratory, it is of course most practical if one CRP method can be used for the complete measuring range (0.2–1000 mg/L) to report reliable CRP results regardless of the clinical context. We report here the evaluation of a hs-CRP method for the Beckman Coulter IMMAGE®, which is compared with the IMMULITE and BNA hs-CRP methods, as well as with the Beckman Synchron LX®20 CRP method for the higher range. Venous blood samples were collected from 291 ostensibly healthy blood donors, 177 males and 114 females presenting at the Sanguin Blood Bank in Maastricht. Samples for method comparison were collected from 531 patients for whom a CRP was requested for routine analysis. The Medical Ethical Committee of the Hospital approved the procedure followed. Serum was separated from the red cells by centrifugation at 2500 g for 20 min and stored at −70 °C until analysis (4). The hs-CRP detection method on the IMMULITE automated analyzer (Diagnostic Product Corporation) is a two-site chemiluminescent enzyme immunometric assay with a detection limit of 0.10 mg/L and a measuring range of 0.10–500 mg/L. hs-CRP analysis is performed on the BNA nephelometer (Dade Behring) by particle-enhanced immunonephelometry with a detection limit of 0.18 mg/L and a measuring range of 0.18–1150 mg/L. The IMMAGE hs-CRP (trade name, IMMAGE CRPH; Beckman Coulter) is a turbidimetric method based on the peak rate principle (2) measured by a near-infrared particle immunoassay, with a laser diode at 940 nm, a detection limit of 0.20 mg/L, and a measuring range of 0.20–1440 mg/L. To improve sensitivity, the latex particle size is now increased three- …