Systematic review and meta-analysis of the prognosis and prognostic factors of interstitial pneumonia with autoimmune features

OBJECTIVE: To clarify the prognosis and prognostic factors of interstitial pneumonia with autoimmune features (IPAF) in comparison to idiopathic pulmonary fibrosis (IPF), the most common idiopathic interstitial pneumonia, and connective tissue disease-associated interstitial pneumonia (CTD-IP). DESIGN: A systematic review and meta-analysis. DATA SOURCES: Electronic databases such as Medline and Embase were searched from 2015 through 6 September 2019. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Primary studies that comparatively investigated the prognosis or prognostic factors of IPAF were eligible. DATA EXTRACTION AND ANALYSIS: Two reviewers extracted relevant data and assessed the risk of bias independently. A meta-analysis was conducted using a random-effects model. The quality of presented evidence was assessed by the Grades of Recommendation, Assessment, Development, and Evaluation system. RESULTS: Out of a total of 656 records retrieved, 12 studies were reviewed. The clinical features of IPAF were diverse between studies, which included a radiological and/or pathological usual interstitial pneumonia (UIP) pattern of between 0% and 73.8%. All studies contained some risk of bias. There was no significant difference of all-cause mortality between IPAF-UIP and IPF in all studies, although the prognosis of IPAF in contrast to IPF or CTD-IP varied between studies depending on the proportion of UIP pattern. Among the potential prognostic factors identified, age was significantly associated with all-cause mortality of IPAF by a pooled analysis of univariate results with a hazard ratio (HR) of 1.06 (95% confidence interval (CI) 1.04 to 1.07). The adjusted effect of age was also significant in all studies. The quality of presented evidence was deemed as very low. CONCLUSION: There was no significant difference of all-cause mortality between IPAF-UIP and IPF. Age was deemed as a prognostic factor for all-cause mortality of IPAF. The findings should be interpreted cautiously due to the low quality of the presented evidence. PROSPERO REGISTRATION NUMBER: CRD42018115870.