An automated C4b binding protein assay compared with an electroimmunoassay in a clinical material

We have evaluated an automated, simplified, turbidimetric method for the measurement of the C4b binding protein (C4bBP). A comparison with a manually performed electroimmunoassay in plasma samples referred for coagulation analysis (n = 80) revealed a correlation coefficient of 0.88. Lipaemic plasma is not suitable for analysis, whereas moderately haemolytic or icteric plasma may be used with the present method. In young and middle-aged patients (n = 33) investigated 3 or more months after an episode with thrombosis of unknown reason, the mean C4bBP concentration was not significantly different from the mean found in healthy controls (n = 38). This result is in accordance with the hypothesis that C4bBP is an acute phase reactant. The results indicate that the turbidimetric assay may replace the electroimmunoassay in clinical work.