Association of anti-nuclear matrix protein 2 antibody with complications in patients with idiopathic inflammatory myopathies: A meta-analysis of 20 cohorts.

Background: Several complications like calcinosis, interstitial lung disease (ILD) or malignancy, are primary causes leading to poor outcomes in idiopathic inflammatory myopathies (IIM) patients. Specific antibodies might help to indicate the occurrence or absence of these complications.

Objective: The aim of this study was to evaluate the association of anti-nuclear matrix protein 2 antibody (anti-NXP2) with calcinosis, ILD and malignancy in IIM patients.

Methods: Two investigators independently searched literature about the relation of anti-NXP2 with calcinosis, ILD, malignancy in IIM patients in PubMed, EMBASE, Web of Science databases, then selected eligible articles and extracted data from the included studies. The association between anti-NXP2 and these complications was assessed by odds ratios (OR) and 95% confidence intervals (95% CI). Further quantitative meta-analysis, subgroup analysis, sensitivity analysis and publication bias analysis were conducted with STATA 14.0 software (Stata Corp.; College Station, Texas, USA). A fixed-effects model (the Mantel-Haenszel method) was employed when I < 25%, otherwise a random-effects model (the Mantel-Haenszel method) was used.

Results: Twenty cohorts with 3064 IIM patients were included in this meta-analysis, among which 9 were about calcinosis in adults, 6 about calcinosis in juvenile patients, 9 about ILD in adults, 3 about ILD in juvenile patients, while 13 about malignancy in adult patients. Anti-NXP2 was more common in patients with calcinosis than those without calcinosis (pooled OR = 4.00, 95% CI: 2.65-6.06 in adults; pooled OR = 1.62, 95% CI: 1.14-2.30 in juvenile patients). On the contrary, this antibody was less common in adult patients with ILD than those without ILD (pooled OR: 0.33, 95% CI: 0.19-0.56). No significant difference concerning the incidence of anti-NXP2 antibody was found in IIM patients between those with and without cancer (pooled OR = 1.42, 95% CI: 0.69-2.91).

Conclusion: The present study indicates that anti-NXP2 autoantibody is a risk factor for development into calcinosis both in adult and juvenile patients, while a protective factor for ILD in adult patients. Anti-NXP2 had no relation with malignancy in adult patients.