Objective. Serological testing for myositis-specific or associated autoantibodies [myositis-specific antibody (MSA) and myositis-associated antibody (MAA)] is useful for the diagnosis of idiopathic inflammatory myopathies (IIMs). However, available assays are neither standardized nor validated. The objective is to evaluate the accuracy of a commercial line blot assay for myositis diagnosis. Methods. IgG antibodies against Jo-1, PL-7, PL-12, PM/Scl, Ku, Mi-2 and Ro52 antigens were detected by a line blot and in-house RNA immunoprecipitation or immunoblot. We tested sera from 208 IIM patients, 50 healthy subjects and 180 control patients (11 non-autoimmune myopathy, 23 muscular dystrophy, 11 UCTD, 68 SLE, 36 SSc, 22 SS and 9 arthropathy). Results. MSAs or MAAs were detected in 98 (47\%) out of the 208 IIM patients by line blot: anti-Jo-1 in 43 (21\%), anti-PL-7 or anti-PL-12 in 8 (4\%), anti-Mi-2 in 9 (4\%), anti-PM/Scl in 9 (4\%), anti-Ku in 10 (5\%) and anti-Ro52 in 49 (24\%). Overall specificity was: 100\% for anti-Jo-1, anti-PL-7 or PL-12 and anti-PM/Scl; 96\% for anti-Ku; 98\% for anti-Mi-2; and 76\% for anti-Ro52. In-house testing confirmed line blot results regarding anti-Jo-1, anti-PM/Scl and anti-Ku, while it was more accurate than line blot in detecting anti-Mi-2 (7 vs 4\% sensitivity, 100 vs 98\% specificity), and anti-aminoacyl-tRNA synthetase (anti-ARS) non-Jo-1 antibodies (11 vs 4\% sensitivity, 97 vs 99\% specificity). Conclusions. Line blot could be a suitable serological test in the diagnostic workup for myositis, and it represents a reliable alternative to more time-consuming procedures. Continuous effort is recommended in order to improve its accuracy.
Diagnostic performance and validation of autoantibody testing in myositis by a commercial line blot assay.
VATTEMI, Gaetano Nicola;
2010-01-01
Abstract
Objective. Serological testing for myositis-specific or associated autoantibodies [myositis-specific antibody (MSA) and myositis-associated antibody (MAA)] is useful for the diagnosis of idiopathic inflammatory myopathies (IIMs). However, available assays are neither standardized nor validated. The objective is to evaluate the accuracy of a commercial line blot assay for myositis diagnosis. Methods. IgG antibodies against Jo-1, PL-7, PL-12, PM/Scl, Ku, Mi-2 and Ro52 antigens were detected by a line blot and in-house RNA immunoprecipitation or immunoblot. We tested sera from 208 IIM patients, 50 healthy subjects and 180 control patients (11 non-autoimmune myopathy, 23 muscular dystrophy, 11 UCTD, 68 SLE, 36 SSc, 22 SS and 9 arthropathy). Results. MSAs or MAAs were detected in 98 (47\%) out of the 208 IIM patients by line blot: anti-Jo-1 in 43 (21\%), anti-PL-7 or anti-PL-12 in 8 (4\%), anti-Mi-2 in 9 (4\%), anti-PM/Scl in 9 (4\%), anti-Ku in 10 (5\%) and anti-Ro52 in 49 (24\%). Overall specificity was: 100\% for anti-Jo-1, anti-PL-7 or PL-12 and anti-PM/Scl; 96\% for anti-Ku; 98\% for anti-Mi-2; and 76\% for anti-Ro52. In-house testing confirmed line blot results regarding anti-Jo-1, anti-PM/Scl and anti-Ku, while it was more accurate than line blot in detecting anti-Mi-2 (7 vs 4\% sensitivity, 100 vs 98\% specificity), and anti-aminoacyl-tRNA synthetase (anti-ARS) non-Jo-1 antibodies (11 vs 4\% sensitivity, 97 vs 99\% specificity). Conclusions. Line blot could be a suitable serological test in the diagnostic workup for myositis, and it represents a reliable alternative to more time-consuming procedures. Continuous effort is recommended in order to improve its accuracy.
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