Limitations of immune complex measurements in colorectal disease

Three techniques (Clq, Raji and L1210 binding assays) alleged to measure circulating immune complexes (ICs) were applied to the sera of 101 patients with colorectal disease (54 carcinoma; 23 inflammatory; 13 benign tumour and 11 miscellaneous) at the time of diagnostic or definitive surgery, and 58 healthy adult controls. Elevated levels in the pathological sera were observed by all 3 methods in order of sensitivity: Raji greater than Clq greater than L1210. However, none of them differentiated between benign, inflammatory and neoplastic conditions nor, in the case of colorectal carcinoma, was there any correlation with stage of disease. With the exception of Raji v. L1210 (r = 0.43, P less than 0.001), correlations between the various assays were poor and levels of serum carcinoembryonic antigen (CEA) did not correlate with ICs measured by any of the techniques. Indeed, the IC assays were even less discriminatory than CEA, which was elevated mainly in the serum of carcinoma patients and which was positively correlated with serum gamma-glutamyl transpeptidase (gamma GT) (r = 0.42, P less than 0.005). The data suggest that the lack of concordance between the IC assays is a reflection of heterogeneity among ICs, interfering factors present in pathological sera, or both. Thus the IC assays deployed here have neither diagnostic nor prognostic utility in colorectal disease at this time, and immunochemical characterization of the serum reactive material detected by the different assays is required.