Department of Translational Medicine, Section of Internal and Cardio Respiratory Medicine, University of Ferrara, 44124 Ferrara, Italy. Department of Cardiology, Rovigo General Hospital, 45100 Rovigo, Italy. Department of Medicine, Casa di Cura Porto Viro, 45014 Rovigo, Italy. Department of General Surgery, Santa Maria degli Angeli Hospital, 06081 Adria, Italy.
INTRODUCTION The prevalence and prognostic implications of anemia in patients infected by the SARS-CoV-2 remains unclear. We performed a systematic review and meta-analysis to assess the prevalence and mortality risk in COVID-19 patients with anemia. METHODS Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed in abstracting data and assessing validity. We searched MEDLINE and Scopus to locate
all the articles published up to 1 September 2021, reporting data on the adjusted OR (aOR) for mortality among COVID-19 patients with anemia. The pooled prevalence of anemia among COVID-19 patients was calculated using a random effects model and presenting the related 95% confidence interval (CI), while the mortality risk was estimated using the Mantel-Haenszel random effects models with odds ratio (aOR) and related 95% CI. Statistical heterogeneity was measured using the Higgins I(2) statistic. RESULTS Five studies, enrolling 9.623 COVID-19 patients [3.707 males (38.5%)], met the inclusion criteria and were included in the final analysis. The pooled prevalence of anemia was 25.6% of cases (95% CI: 8.3-56.5%), with high heterogeneity (I(2) = 98.9%). Meta-regression showed that the anemia prevalence was influenced by a direct correlation with age (p = 0.007) and chronic kidney disease (p = 0.004) as moderating variables. Conversely, an inverse relationship was observed with male gender (p < 0.0001). Anemia was significantly associated with higher risk of short-term mortality (aOR: 1.69, 95% CI: 1.28-2.24, p < 0.001), with low heterogeneity (I(2) = 0%). CONCLUSIONS Anemia represents a major comorbidity in about 25% of COVID-19 patients and it is associated with about 70% higher risk of short-term mortality.
