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

Abstract

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; I2 = 85.6%) for all 56 studies. The 1-year SMR in the US was 2.40 (95% CI, 0.89-3.90; I2 = 86.3%) for 3 studies; in Asia, 3.53 (95% CI, 2.85-4.20; I2 = 86.3%) for 16 studies; and in Europe, 2.77 (95% CI, 2.35-3.19; I2 = 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.