Anti-Jo-1 antibodies in polymyositis or dermatomyositis: evaluation by ELISA using recombinant fusion protein Jo-1 as antigen.

We evaluated an enzyme-linked immunosorbent assay (ELISA) for detecting anti-Jo-1 antibodies in patients with polymyositis (PM) or dermatomyositis (DM) by use of the recombinant fusion protein Jo-1. Sera from 64 patients with PM or DM, from 80 patients with other connective tissue diseases, and from 64 healthy subjects matched for age, sex and race, were studied by the ELISA and by the double immunodiffusion (DID) method. Eight patients with myositis (six PM, one DM and one DM with malignancy) with positive anti-Jo-1 by DID also showed positive results by the ELISA method, whereas five patients with positive anti-Jo-1 by this ELISA showed negative results on DID. One of the five had non-specific results. The incidence of positive results for anti-Jo-1 with the ELISA (18.8%) was greater than that for DID (12.5%), but the difference was not statistically significant. All patients with positive results for anti-Jo-1 by DID were also positive by the ELISA. The ELISA system with the recombinant Jo-1 antigen was useful in the detection of anti-Jo-1 antibodies in patients with PM/DM.