Sensitivity and specificity of immunological methods for the detection of anti-topoisomerase I (Sc170) autoantibodies: Results of a multicenter study

Abstract

Background: The ability of immunometric methods to identify anti-topoisomerase I (Scl70) antibodies is controversial. We wished to quantify the performance of the currently available commercial systems for the assay of anti-topoisomerase 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 group. The scleroderma/systemic sclerosis samples were positive in our laboratories by both ELISA and immunoblot (IB), and the control samples were negative. The laboratories used 42 immunoenzymatic (ELISA), 21 IB, 3 counterimmunoelectrophoresis, and 2 dot-blot methods, produced by 23 different manufacturers. Results: We obtained 2389 results. The ELISA methods showed 99.2% specificity and 97.2% sensitivity for detection of anti-Scl70 antibodies. For IB methods, specificity was 97.6% and sensitivity was 96.1%. The Western-blot method had poor analytical specificity (27% false positives for anti-extractable nuclear antigen antibodies other than anti-Scl70). Conclusions: Excluding Western blots, commercial ELISA and IB reagents as used in clinical laboratories have a sensitivity and a specificity >95% for determination of anti-Scl70 antibodies. (C) 2000 American Association for Clinical Chemistry.