Measurement of proteins with the Behring Nephelometer. A multicentre evaluation.

The selective multi-protein analyser Behring Nephelometer was examined according to the ECCLS guidelines in a multicentre evaluation involving five laboratories. IgG, IgA, IgM, C-reactive protein, C3c, C4, apolipoprotein A-I and B were measured in serum, and albumin and IgG were measured in cerebrospinal fluid. All values obtained were included in the evaluation without correcting for outliers. The trial, which lasted three months and involved over 20,000 analyses, basically yielded the following results: 1. The precision was generally better than that of comparative procedures. For the majority of methods, the between-day coefficients of variation were below 4.5%. The highest coefficient of variation was 7.2% (for C-reactive protein) and the lowest 1.35% (for C3c). 2. The fraction of assigned values of control materials varied between 0.95 and 1.08. 3. Good agreement was found with results from the comparison procedures: Beckman ICS, Behring Laser Nephelometer, Hyland Laser Nephelometer. 4. No carry-over effects were observed. 5. No interferences were observed for IgG, IgA and IgM determinations using hyperbilirubinaemic or haemolytic samples. In contrast lipaemic samples and some with monoclonal immunoglobulin M showed an influence on the immunoephelometric reaction. 6. Because of the large measuring range, it is necessary to repeat analyses only in extremely rare cases. 7. During the entire evaluation period no instrument malfunctions or interruptions occurred. As a result of its reliability, the Behring Nephelometer is well suited for routine operation and emergency analyses in medium and large-sized laboratories.