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Letter: hepatitis B virus infection and risk of multiple myeloma—a meta‐analysis of cohort studies

Editors, We read with great interest the recent large-scale cohort study by Su et al1 reporting that chronic hepatitis B virus (HBV) infection is an independent risk factor for multiple myeloma (MM) (hazard ratio: 1.63, 95% confidence interval [CI]: 1.10-2.42, P = 0.016). Given the high prevalence of hepatitis B worldwide and inconsistent results in previous studies,2,3 we conducted a meta-analysis of cohort studies to summarise the association between hepatitis B and the risk of MM. Two authors independently reviewed published studies in PUBMED and EMBASE from inception to October 2019 using a search strategy that included the terms for “hepatitis B” and “myeloma”. We also performed a manual search for additional studies using references of selected retrieved articles to identify other possible studies and a search of conference proceedings. No limitation on language was applied. We included “cohort studies” reporting an association between hepatitis B and MM incidence and providing related data as hazard ratio or equivalents with 95% CI. Two authors independently performed data extraction using a pre-designed form. Disagreement was resolved by discussion among all investigators. The analysis was performed by Stata14.0 software (StataCorp). In view of the predictable heterogeneity among studies, random-effects model was used. Of 346 potentially relevant published studies, 339 were excluded due to duplication (n = 76) or article types (n = 112) or because the title and abstract did not meet the inclusion criteria (n = 151). One additional article was excluded for unextractable results.4 Finally, six cohort studies including the study by Su et al met all inclusion