An improved turbidimetric assay for the measurement of C-reactive protein (CRP) has been evaluated in six laboratories on various analytical systems (Boehringer Mannheim Hitachi systems 704, 717, 747, 911, 917 and on Keysys® analyzer). Compared to the previous test version this assay has better transferability of results from instrument to instrument, less lipemia and gammopathy interference, a better linearity in the lower concentration range, the applicability of EDTA plasma or heparin plasma and a satisfactory recovery of target values according to CRM 470 standardization. The detection limit of the Tina-quant® CRP assay is 1.9 mg/l CRP. Median values of CVs within run of lower than 2.5% and between day of lower than 3.3% were obtained. A survey with 50 human pool sera revealed a good transferability of results obtained in different laboratories and on different analytical systems. Method comparison studies between the Tina-quant® CRP assay and fixed-time nephelometry, rate nephelometry and turbidimetry were in reasonable agreement (± 10%) throughout the entire measuring range. No drift effect was noticed with the tubing system on Boehringer Mannheim/Hitachi 747 analyzers. The reagent and calibration stability was extended to 12 weeks. The Tina-quant® CRP assay enables the precise, accurate, rapid and convenient determination of CRP used for routine clinical chemistry and STAT purposes.
Hafner, G., Thomas, L., Borque de Larrea, L., Galanti, L., Ilardo, C., Scheurmann, T., Roddiger, R., & Zawta, B. (1997). Determination of C-Reactive protein by an improved turbidimetric assay. Laboratoriums-Medizin : journal of laboratory medicine, 21(12), 659-666. https://hdl.handle.net/2078.5/86266 (Original work published 1997)