Systematic review and meta-analysis of prognostic factors for idiopathic inflammatory myopathy-associated interstitial lung disease

Objective: To clarify prognostic factors for idiopathic inflammatory myopathy (IIM)-associated interstitial lung disease (ILD). Design: Systematic review and meta-analysis using the Grades of Recommendation, Assessment, Development and Evaluation system. Data sources: Medline, EMBASE and Science Citation Index Expanded were searched through 9 August 2018. Eligibility criteria for selecting studies: The review includes primary studies addressing all-cause mortality of IIM-associated ILD. Potential prognostic factors were any clinical information related to the outcome. Data extraction and synthesis: Two reviewers extracted relevant data independently and assessed risk of bias using the Quality in Prognostic Studies tool. Meta-analysis was conducted using a random effects model and if inappropriate the results were reported qualitatively. Prognostic factors were determined based on statistically significant results derived from multivariate analysis. Results: Of a total of 5892 articles returned, 32 were deemed eligible for analysis and cumulatively, these studies reported 28 potential prognostic factors for all-cause mortality. Each study was subject to certain methodological constraints. The four prognostic factors, which demonstrated statistically significant results on both univariate and multivariate analyses, were as follows: age (MD 5.90, 3.17-8.63/HR 1.06, 1.02-1.10 and 2.31, 1.06-5.06), acute/subacute interstitial pneumonia (A/SIP) (OR 4.85, 2.81-8.37/HR 4.23, 1.69-12.09 and 5.17, 1.94-13.49), percentage of predicted forced vital capacity (%FVC) (OR 0.96, 0.95-0.98/HR 0.96, 0.93-0.99) and anti-Jo-1 antibody (OR 0.35, 0.18-0.71/HR 0.004, 0.00003-0.54) (univariate/multivariate, 95% CI). Other prognostic factors included ground glass opacity/attenuation (GGO/GGA) and extent of radiological abnormality. The quality of the presented evidence was rated as either low or very low. Conclusions: Older age, A/SIP, lower value of %FVC, GGO/GGA and extent of radiological abnormality were demonstrated to predict poor prognosis for IIM-associated ILD while a positive test for anti-Jo-1 antibody indicated better prognosis. However, given the weak evidence they should be interpreted with caution.