Sensitivity and specificity of immunological methods for the detection of anti-topoisomerase I (Scl70) autoantibodies: Results of a multicenter study

Background: The ability of immunometric methods to identify anti-topoisomer ase I (Scl70) antibodies is controversial. We wished to quantify the perfor mance of the currently available commercial systems for the assay of anti-t opoisomerase I antibodies in a large multicenter study. Methods: Fifty Italian clinical laboratories analyzed 36 serum samples: 27 from individuals with scleroderma/systemic sclerosis and 9 from a control g roup. The scleroderma/systemie sclerosis samples were positive in our labor atories by both ELISA and immunoblot (IB), and the control samples were neg ative. The laboratories used 42 immunoenzymatic (ELISA), 21 IB, 3 counterim munoelectrophoresis, and 2 dot-blot methods, produced by 23 different manuf acturers. Results: We obtained 2389 results. The ELISA methods showed 99.2% specifici ty and 97.2% sensitivity for detection of anti-Scl70 antibodies. For IB met hods, specificity was 97.6% and sensitivity was 96.1%. The Western-blot met hod had poor analytical specificity (27% false positives for anti-extractab le nuclear antigen antibodies other than anti-Scl70). Conclusions: Excluding Western blots, commercial ELISA and IB reagents as u sed in clinical laboratories have a sensitivity and a specificity >95% for determination of anti-Scl70 antibodies. (C) 2000 American Association for C linical Chemistry.