Development of a single numerical expression for the results of multiple screening tests for immune complexes in diabetic patients: use in statistical comparison of clinically and biochemically defined patient populations.

A series of 88 diabetic patients were studied for the presence of soluble immune complexes, proteinuria, microangiopathy, and diabetic complications. Results of the five different assays for immune complexes were analyzed individually, and four combinations of the individual results (i.e. four different immune complex "scores") were also analyzed. The only assay which consistently discriminated between the different patient groups was the PEG-IgG test, in which a ratio between the amount of IgG precipitated with 3% PEG 6000 and the serum concentration of IgG is determined. In contrast, all four of the immune complex "scores" detected significant differences between patients with and without the clinical or biochemical parameter in question. One combination, designated as the "weighted and corrected IC score", gave a particularly high probability of detecting differences between groups. These results indicate that proper compilation of the results of a battery of immune complex screening assays can provide definite advantages over the results of individual tests for the investigation of correlations between the presence of soluble immune complexes and the course and pathology of various diseases.