Anti-TIF1γ antibodies (anti-p155) in adult patients with dermatomyositis: comparison of different diagnostic assays.

Abstract

A new myositis-specific autoantibody (anti-p155) directed against transcriptional intermediary factor 1 γ (TIF1γ) has been described as a good marker of cancer-associated myositis (CAM). To analyse the feasibility of detecting this autoantibody in patient serum samples using new assays with commercially available recombinant TIF1γ. The study included 90 Spanish patients with dermatomyositis (DM), classified as clinically amyopathic DM, CAM, or DM without cancer. Anti-TIF1γ antibodies were detected by ELISA and immunoblot techniques and compared with anti-p155 antibody detection by protein immunoprecipitation assays with radiolabelled HeLa cells. The κ coefficient was used to compare the agreement between the different tests. Serum samples from 23 (25.6%) and 20 (22.2%) patients with DM recognised TIF1γ by ELISA and immunoblot, respectively. ELISA (κ=0.91) and immunoblot (κ=0.88) showed excellent agreement with immunoprecipitation analysis (anti-p155). Good concordance (κ=0.91) was also seen between ELISA and immunoblot. Excellent agreement was found between anti-p155 detected by immunoprecipitation and anti-TIF1γ detected by ELISA or immunoblot. These data indicate that identification of this autoantibody can be reliably performed in a standard laboratory setting, with potential application in clinical practice for cancer screening in adult patients with DM.