Anemia in patients with hidradenitis suppurativa A systematic review with meta-analysis

Importance Hidradenitis suppurativa (HS) is associated with a number of physical and psychological comorbidities. Studies have suggested an association between HS and anemia; however, this association is not widely understood and may result in delayed diagnosis and treatment and possible increase in morbidity and mortality. Objective To systematically review and perform a meta-analysis regarding the association between HS and anemia, and to characterize the subtypes of anemia associated with HS. Data sources A search of the EMBASE, Medline, Web of Science Core Collection, and Cochrane Central Register of Controlled Trials databases from the time of database inception to September 25, 2022, yielded 313 unique articles. Study selection All observational studies and randomized controlled trials published in English that examined the odds ratio (OR) of anemia in patients with HS were screened by 2 independent reviewers. Case reports were excluded. Among 313 unique articles, 7 were deemed eligible. Data extraction and synthesis The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines facilitated data extraction. The Newcastle-Ottawa Scale (NOS) was used to analyze risk of bias of included studies. In addition to OR and 95% confidence intervals, relevant data on patient demographics and anemia subtypes were also extracted. Main outcomes and measures The primary outcome was the OR of anemia in HS patients. This study also attempted to characterize anemia subtypes associated with HS. Results In total, 2 case-control and 5 cross-sectional studies featured a total of 11,693 patients. Among the studies, 4 of 7 demonstrated a statistically significant positive association between anemia and HS (ORs, 2.20 [1.42-3.41], 2.33 [1.99-2.73], 1.87 [1.02-3.44], and 1.50 [1.43-1.57]), with macrocytic and microcytic subtypes being most common. After adjusting for publication bias, meta-analysis with random effects revealed HS to be associated with increased odds of anemia compared to non-HS groups (OR 1.59 [1.19, 2.11]). Conclusions and relevance There is a statistically significant positive association between HS and anemia, particularly for the aforementioned subtypes. Patients with HS should be screened for anemia. In case of lower hemoglobin concentration, the anemia of HS patients should be subdivided according to mean corpuscular volume of the red blood cells and further investigated depending on subtype.