Prevalence and Risk Factors of Relapse in Pulmonary Sarcoidosis: First Systematic Review and Meta-Analysis

Background and Aim: Relapses are known to adversely affect the prognosis of patients with pulmonary sarcoidosis (PS). However, a systematic review or meta-analysis on the subject is not yet available in the literature. Research question: What are the global prevalence and risk factors for relapse in PS patients? Methods: We systematically searched PubMed, Google Scholar, Scopus, and Embase electronic databases to collect eligible PS studies published until 31 January 2025. Eligible studies were peer-reviewed, English-language studies reporting relapse and risk factors in PS patients. Prevalence and risk factors were analyzed using proportions and log odds ratios (LORs) with 95% confidence intervals (CIs). Quality was assessed by Hoy et al tool for prevalence studies Results: A total of 50 studies with 5978 patients were included in this meta-analysis. Among these patients, 3646 were followed up, and PS relapse was analyzed. Relapse prevalence heterogeneity was significant (Q test, p<0.01). The pooled prevalence of relapse was 0.40 (95% CI: 0.34, 0.46) in all included studies. Sensitivity analyses of the pooled prevalence estimate showed minimal variation, with estimates ranging from 35% to 41% across analyses removing outliers, performing leave-one-out, adjusting for study size, excluding lower-quality studies, and excluding studies without relapse definitions. The pooled prevalence of relapse in prospective vs. retrospective studies was 0.32 (95% CI: 0.26, 0.38) vs. 0.44 (95% CI: 0.36, 0.54), with a meta-regression coefficient of 0.14 (p = 0.02). The pooled LOR of relapse was greater for patients who were black [0.91 (95% CI: 0.44, 1.37); p<0.001], had stage II & III disease [0.55 (95% CI: 0.07, 1.03); p=0.02], and had stage IV disease [1.04 (95% CI: 0.25, 1.83); p=0.01], whereas it was comparable for age, sex, treatment type, and PS type (isolated or systemic PS). Conclusion: The pooled prevalence of PS relapse in all studies was 40%, but it was lower in prospective studies. A black race and higher-grade radiographic stages were the underlying risk factors for disease relapse.