An evaluation of immunoglobulin assays on the ACA III.

We evaluated an immunoturbidimetric Du Pont ACA method for the determination of IgG, IgA and IgM in serum. Between-day reproducibilities of the ACA assays were comparable to those of a radial immunodiffusion, a Hyland nephelometric and a turbidimetric assay on Centrifichem 400. Correlations between results obtained by these methods were acceptable, but the results differed quantitatively. After simulated recalibration based on results of control sera or patient samples, the results for IgA and IgM became more interchangeable. IgM concentrations below 0.25 g/l, which are important for the assessment of intra-uterine infections, could not be quantified with the ACA. Moderate levels of haemoglobin, bilirubin or lipids do not interfere with the ACA assays. The evaluated assays are fast and easy to use.

Two serum pancreatic isoamylase determinations compared.

Serum pancreatic isoamylase activity was measured by a method involving inhibition of salivary isoamylase and by a well-known agarose electrophoretic method, modified by us. We saw changes in electrophoretic patterns of pancreatic isoamylase fractions after storage of serum samples for three weeks at 4-8 degrees C, but with the inhibition method no alterations in activities were found. Within-assay and between-assay imprecisions of both methods were about the same. Serum pancreatic amylase activities as measured by the inhibition method exceeded by about 10% those obtained by the electrophoretic method. The inhibition method seems to be a reasonable candidate for routine application, whereas the electrophoretic method is still time-consuming and requires special skill to perform. Some suggestions are given for improving the calibration of the inhibition method recommended by the manufacturer.