M Infantino1, M Tampoia2, M Fabris3, M G Alessio4, G Previtali4, G Pesce5, G Deleonardi6, B Porcelli7, M Musso8, V Grossi1, M Benucci9, M Manfredi1, N Bizzaro10. 1. Laboratorio Immunologia e Allergologia, Ospedale S. Giovanni di Dio, Firenze, Azienda USL Toscana Centro, Italy. 2. Laboratorio di Patologia Clinica, Azienda Ospedaliera Universitaria, Policlinico di Bari, Bari, Italy. 3. SOC Istituto di Patologia Clinica, Azienda Sanitaria Universitaria Integrata di Udine, Udine, Italy. 4. Laboratorio Analisi Chimico Cliniche ASST Papa Giovanni XXIII, Bergamo, Italy. 5. Lab. Autoimmunologia e Coordinamento con la clinica, Di.M.I. Università degli Studi di Genova, Genova, Italy. 6. Laboratorio Unico Metropolitano, AUSL Bologna, Bologna, Italy. 7. Dipartimento Biotecnologie Mediche, Università degli Studi di Siena, Siena, Italy. 8. Laboratorio Analisi ASO S.Croce e Carle, Cuneo, Italy. 9. Reumatologia, Ospedale S. Giovanni di Dio, Firenze, Azienda USL Toscana Centro, Italy. 10. Laboratorio di Patologia Clinica, Ospedale San Antonio, Tolmezzo, Italy, Italy.
Abstract
OBJECTIVE: Immunoblot (IB) methods are widely used to detect myositis-specific autoantibodies (MSAs); however, false-positive results are common. In this study, we aimed to determine whether associating the anti-nuclear antibody (ANA) IIF pattern may help to improve the specificity of MSA detection by IB in patients with idiopathic inflammatory myositis (IIM). METHODS: Serum samples from 104 patients presenting with muscle weakness/myalgia and positive to at least one MSA by IB (MYOS12 Diver and MIOS7 Diver, D-tek) were tested for ANAs on HEp-2000 cells (Immuno Concepts). The chi-square test was used to analyse the concordance of the MSA result and its corresponding pattern by ANA testing between patients with and without IIM. RESULTS: Eighty-three of the 104 patients had a diagnosis of definite IIM, while in 21 cases, patients were affected by other autoimmune diseases or various non-systemic diseases. Forty nine of 83 (59%) patients in the IIM group and 4/21 (19%) in the non-IIM group showed a concordance between ANA pattern and MSAs by IB (P < 0.001). MSA monopositivity was significantly associated with IIM (91.6%) compared with 61.9% in the non-IIM group (P = 0.0005). CONCLUSIONS: Considering both the MSA result and its corresponding pattern by ANA testing may help to improve the specificity of MSA detection by IB and to confirm the diagnosis of MSA-associated IIM. The monopositivity of MSAs is an important additional tool to validate IB results.
OBJECTIVE: Immunoblot (IB) methods are widely used to detect myositis-specific autoantibodies (MSAs); however, false-positive results are common. In this study, we aimed to determine whether associating the anti-nuclear antibody (ANA) IIF pattern may help to improve the specificity of MSA detection by IB in patients with idiopathic inflammatory myositis (IIM). METHODS: Serum samples from 104 patients presenting with muscle weakness/myalgia and positive to at least one MSA by IB (MYOS12 Diver and MIOS7 Diver, D-tek) were tested for ANAs on HEp-2000 cells (Immuno Concepts). The chi-square test was used to analyse the concordance of the MSA result and its corresponding pattern by ANA testing between patients with and without IIM. RESULTS: Eighty-three of the 104 patients had a diagnosis of definite IIM, while in 21 cases, patients were affected by other autoimmune diseases or various non-systemic diseases. Forty nine of 83 (59%) patients in the IIM group and 4/21 (19%) in the non-IIM group showed a concordance between ANA pattern and MSAs by IB (P < 0.001). MSA monopositivity was significantly associated with IIM (91.6%) compared with 61.9% in the non-IIM group (P = 0.0005). CONCLUSIONS: Considering both the MSA result and its corresponding pattern by ANA testing may help to improve the specificity of MSA detection by IB and to confirm the diagnosis of MSA-associated IIM. The monopositivity of MSAs is an important additional tool to validate IB results.
Authors: Julia Graham; Iazsmin Bauer Ventura; Chad A Newton; Cathryn Lee; Noelle Boctor; Janelle Vu Pugashetti; Claire Cutting; Elena Joerns; Habrinder Sandhu; Jonathan H Chung; Christine Kim Garcia; Michael Kadoch; Imre Noth; Ayodeji Adegunsoye; Mary E Strek; Justin M Oldham Journal: Eur Respir J Date: 2020-07-16 Impact factor: 16.671