[Serum levels of IgG, IgA, IgM, transferrin and haptoglobin. II. Analytical precision and comparison of results from different analysers].

We compare the precision of immunochemical techniques for determining immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin M (IgM), transferrin and haptoglobin. Precision was found satisfactory. Results of samples containing monoclonal Ig, showed substantial discrepancies, especially the serum containing monoclonal IgM. In this case, the nephelometric analysers gave the best results. In conclusion, when different techniques are used for monitoring protein immunoassays, a good knowledge of the performance of the analyser is necessary for correct interpretation and to avoid potentially misleading results.