Basic characteristics and evaluation of a partially automated Behring laser nephelometer for the measurement of IgG, IgA, IgM and C3c in serum.

We have evaluated a partially automated Behring laser nephelometer for the measurement of IgG, IgA, IgM and C3c in serum. The system consisted of a manual Behring laser nephelometer, an automatic cuvette carrier and a Hewlett-Packard 9815 A calculator/printer. The system could process 240 preincubated samples per h when the interval between each voltage reading was set at 15 s. Day-to-day precision was near 6%. We obtained the worst precision for the determination of IgG which requires the smallest volume of diluted sample (10 microliters). The Frigen treatment used to clarify turbid sera seems to decrease IgG and increase C3c concentrations. The addition of polyethylene glycol 6000 at a concentrations of 40 micro/L in the reaction mixture did not improve the assay ranges. Comparison studies with radial immunodiffusion for the four proteins and with the IgM - BMC Immunological Turbidity Test using either least-squares or Deming's regressions gave very good correlation figures, except for C3c and for some IgM paraproteins. We could decrease the cost per test by re-using the plastic cuvettes. The utilization of the calculator-printer greatly simplified data handling but the automatic carrier was not considered a real asset without complete automation.