Mixed Individual-Aggregate Data on All-Cause Mortality in Bullous Pemphigoid A Meta-analysis

Abstract

This meta-analysis estimates the 1-year standardized mortality ratio among patients with bullous pemphigoid. Importance The 1-year standardized mortality ratio (SMR) of bullous pemphigoid (BP) has been reported as 2.15 to 7.56 and lower in the US than in Europe. Objective To estimate the worldwide 1-year SMR of BP. Data Sources PubMed, Embase, Cochrane Library, Google Scholar, Lissa, and gray literature (eg, medRxiv) were screened for studies of BP published from inception to June 10, 2020, with review of reference lists. Study Selection Retrospective and prospective studies reporting 1-year all-cause mortality rate in patients with BP and providing age statistics (eg, mean [SD]). Data Extraction and Synthesis Two reviewers independently extracted the data. The 1-year SMR was computed in studies reporting 1-year mortality by combining information on age obtained from studies with aggregate data and individual data. Risk of representativity, misclassification, and attrition bias were assessed by a custom tool. Main Outcomes and Measures The primary end point was the worldwide 1-year SMR. Secondary analysis included comparison of 1-year SMRs between continents in a meta-regression. Results Three studies were performed in the US (n = 260), 1 in South America (n = 45), 16 in Asia (n = 1903), and 36 in Europe (n = 10 132) for a total of 56 unique studies and 12 340 unique patients included in the meta-analysis (mean [SD] age, 77.3 [12.7] years; 55.9% women). The mean (SD) patient age in the United States was 75.6 (13.7) years; in Asia, 73.8 (13.6) years; and in Europe, 78.1 (12.3) years. The worldwide 1-year SMR was estimated at 2.93 (95% CI, 2.59-3.28; I-2 = 85.6%) for all 56 studies. The 1-year SMR in the US was 2.40 (95% CI, 0.89-3.90; I-2 = 86.3%) for 3 studies; in Asia, 3.53 (95% CI, 2.85-4.20; I-2 = 86.3%) for 16 studies; and in Europe, 2.77 (95% CI, 2.35-3.19; I-2 = 86.3%) for 36 studies. After adjustment on the expected 1-year mortality rate, the European 1-year SMR did not differ significantly from the 1-year SMR in the United States (-0.48 vs Europe; 95% CI, -2.09 to 1.14; P = .56) and Asia (0.51 vs Europe; 95% CI, -0.56 to 1.58; P = .35). Risk of attrition bias was high (>10% censorship) in 16 studies (28.6%), low in 16 (28.6%), and unclear in 24 (42.9%). Only 4 studies (7.1%) had a sampling method guaranteeing the representativity of BP cases in a population. Conclusions and Relevance Although heterogeneity was high and overall quality of follow-up was poor, this meta-analysis confirms the high mortality rate among patients with BP. Question Is bullous pemphigoid (BP) associated with increased mortality relative to the general population? Findings This meta-analysis combining individual and aggregate data from 56 unique studies of 12 340 unique patients found that patients with BP had a 2.93-fold increased 1-year mortality rate compared with the general population. Mortality was associated with BP itself, adverse effects of treatment, and/or patients' comorbidities, with infections as the main cause of death. Meaning These findings may help clinicians in the management of BP and suggest avoiding aggressive treatments.