Rapid turbidimetric determination of serum C3c and C4 by end point centrifugal analysis.

An end point turbidimetric method for the determination of C3c and C4 in serum using a centrifugal analyzer (Cobas Bio) is described. Several analytical factors were evaluated -pH, temperature, PEG and antibody concentration. Wide variations of temperature and pH did not significantly affect the turbidimetric reaction. A 20 g/L PEG concentration and 25-fold antiserum dilution were found satisfactory for the analysis. Precision of the assay was good and comparison with a RID method yielded an r value of 0.97. The procedure is simple and reliable.