Evaluation of recombinant Ro/SSA, La/SSB, Sm, and U1 RNP autoantigens in clinical diagnosis.

This study comprises an analysis of the diagnostic usefulness of Ro/SSA, La/SSB, Sm and U1 RNP autoantigens obtained by DNA recombinant technology. We studied the presence of these autoantibodies in 33 patients with systemic lupus erythematosus (SLE) and 30 normal individuals by enzyme-linked immunosorbent assay (ELISA) using recombinant autoantigens and by Western immunoblot with these same antigens obtained from natural sources (rabbit thymus and human spleen). The strength of agreement between results found with these two techniques was moderate in the case of anti-Ro/SSA (kappa = 0.474, P < 0.001) and anti-U1 RNP (kappa = 0.566. P < 0.001) antibodies and almost perfect in the case of anti-La/SSB (kappa = 0871, P < 0.001) and anti-Sm (kappa = 0.833, P < 0.001). Furthermore, analysis of the disagreement between the two techniques evidenced a measurement bias for anti-Ro/SSA and anti-U1 RNP antibodies (Mc NEMAR'S statistic 13 and 11, respectively) whose direction, though difficult to define in the absence of a gold standard for such determinations, could be accounted for by the ELISA technique's greater tendency to produce positive results. Our conclusion is that the diagnostic usefulness of recombinant La/SSB and Sm autoantigens has been satisfactorily proven, whereas the case of the Ro/SSA and U1 RNP systems should be subject to further in-depth study of the autoepitopes recognised and the possible modifications which the latter might undergo as a result of their obtension from procariotic sources.

Hepatitis C virus antibodies and liver disease in patients with porphyria cutanea tarda.

The recent identification of the hepatitis C virus and development of assays to detect antibodies to hepatitis C virus has allowed assessment of the prevalence of hepatitis C virus infection in patients with a variety of liver and other diseases. The aim of this study was to investigate the prevalence of hepatitis C virus antibodies and severity of liver injury in patients with porphyria cutanea tarda. Sixty-two patients were studied. Serum samples were analyzed for liver function parameters and markers of hepatitis B virus infection. Frozen serum samples from 34 patients with porphyria cutanea tarda, obtained when patients were seen at the hospital for the first time, were analyzed for hepatitis C virus antibodies with enzyme-linked immunosorbent assays (first- and second-generation) and a recombinant immunoblot assay. As controls, serum samples from 19,788 blood donors, 40 patients with alcoholic liver disease and 138 hospitalized patients without liver disease were also tested for hepatitis C virus antibodies. Liver biopsy was performed in 42 porphyria cutanea tarda patients. Specimens were evaluated for steatosis, siderosis, fibrosis, severity of inflammation and the presence of cirrhosis. In addition, the degree of necroinflammatory change and fibrosis were quantitated with the histologic activity index described by Knodell et al. The prevalence of hepatitis C virus antibodies in patients with porphyria cutanea tarda (62%) was higher than that in blood donors (0.79%), patients with alcoholic liver disease (17.5%) or hospitalized patients without liver disease (5.8%).(ABSTRACT TRUNCATED AT 250 WORDS)