The use and diagnostic value of testing myositis-specific and myositis-associated autoantibodies by line immuno-assay: a retrospective study

Abstract

Aims: Line immune-assays (LIA) for the detection of myositis-specific antibodies (MSA) are used widely for characterization of idiopathic inflammatory myopathies (IIM). Their current use and significance for the diagnosis of IIM remains unclear. Methods: In this retrospective analysis, we retrieved clinical diagnoses of patients tested for MSA and myositis-associated antibodies (MAA) Jo-1, Mi-2α, Mi-2β, TIF1γ, SRP, MDA-5, NXP-2, SAE, PL-7, PL-12, EJ, OJ, PM-Scl100, PM-Scl75 and Ku. We calculated clinical specificity, clinical sensitivity, negative- and positive predictive values (PPV) as well as positive and negative likelihood ratios. Results: In total, we analyzed 3167 samples. After exclusion of repeated measurements and patients with insufficient clinical information, data of 1118 patients were available for analysis. A total of 242 patients tested positive for at least one antibody, of which 45 patients had a diagnosis of IIM; 25 IIM patients were negative for all MSA/MAA. Clinical specificity of MSA/MAA for the diagnosis of IIM ranged between 94.2% and 99.9%. Clinical sensitivity and PPV across all antibodies tested ranged from 0.0% to 12.9% and 0.0% to 72.7%, respectively. Conclusion: In clinical practice MSA/MAA are used widely for diagnostic work-up of IIM, resulting in a low pre-test probability. Clinicians should be aware that PPVs for most MSA/MAA are low.

Profiling of Myositis Specific Antibodies and Composite Scores as an Aid in the Differential Diagnosis of Autoimmune Myopathies

“…Despite the expansion of MSA as an aid in the diagnosis and stratification of IIM and their global adoption, significant challenges persist, which include the lack of standardization and the difficulty in interpretation of results. Careful validation of autoantibody assays for the detection of MSA is important, since some of these antibodies are included or being considered for IIM classification criteria [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Although several other MSA also carry clinical utility, only anti-Jo-1 antibodies have been included in the recent EULAR/ACR classification criteria for IIM, mostly due to the lack of data and standardization of other MSA.…”

“…In addition, several autoantibodies showed relevance for a novel approach to classify IIM [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Consequently, the markers are not only relevant as an aid in the diagnosis, but also in the stratification to specific disease subsets [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Most of the clinical associations of MSA and MAA have been established using IP and might be lost with newer methods [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 ].…”

“…However, it is evident that LIA or dot blots (DB) have become convenient tools for the simultaneous detection of various antibodies, and some of the markers contained on LIA show good to excellent correlation with IP [ 25 ]. However, LIA and DB are also accompanied by some limitations, including the lack of true quality controls [ 8 , 25 ] and the lack of sensitivity or specificity for some analytes [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Recently, data from different studies were summarized showing varying agreement (from low to high, kappa: PM/Scl, 0.48; Jo-1, 0.52; Mi-2; 0.56; SRP, 0.60; TIF1y, 0.71; PL-12, 0.72; EJ, 0.72; MDA5, 0.75; SAE, 0.79; Ku, 0.83; NXP-2, 0.86; PL7, 0.82).…”

“…Recently, data from different studies were summarized showing varying agreement (from low to high, kappa: PM/Scl, 0.48; Jo-1, 0.52; Mi-2; 0.56; SRP, 0.60; TIF1y, 0.71; PL-12, 0.72; EJ, 0.72; MDA5, 0.75; SAE, 0.79; Ku, 0.83; NXP-2, 0.86; PL7, 0.82). Part of this inter-method variability might be attributed to the subjectivity associated with interpretation [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ] which can be addressed by automated scanning systems [ 11 , 32 ] that allow for a ‘semi-quantitative‘ assessment and thus for the estimation of antibody levels (titers). Due to the lack of correlation between LIA results, IP and IIM phenotypes, Mecoli et al proposed modified cut-offs for the different MSA [ 12 ].…”

“…Since many of the MSA (e.g., anti-synthetase antibodies), partly depending on the screening dilution, are accompanied by limited sensitivity of the indirect immunofluorescence (IIF) test on HEp-2 cells [2][3][4][5], confirmatory tests are used at screening level. At present, besides immunoprecipitation (IP), mostly line immunoassays (LIA) and dot blot (DB) assays are routinely used for the detection of MSA [6], which are convenient tools for the simultaneous detection of various antibodies, but are also accompanied by some limitations [7] including the lack of true quality controls [8], lack of sensitivity [9,10] and specificity (10) for some analytes and subjectivity in interpretation [10][11][12].…”