Anemia and polycythemia in patients hospitalised with acute exacerbations of chronic obstructive pulmonary disease: prevalence, patient characteristics, and risk of readmission and mortality.

Background: Both anemia and polycythemia have previously been shown to influence outcomes in patients with COPD admitted to hospital with acute exacerbations (AECOPD). The aims of this study are to elucidate the prevalence of anemia and polycythemia and their prognostic value on readmission and mortality in patients admitted with AECOPD. Methods: This retrospective cohort study included patients admitted with AECOPD to hospitals in the North Denmark Region in 2018. Age, gender, body mass index, lung function, smoking history, number of comorbidities, hemoglobin levels, information regarding readmission and mortality were included. Patients were stratified according to hemoglobin levels: Anemia (<12 g/dL in women, <13 g/dL in men), normal hemoglobin (12-15 g/dL in women, 13-17 g/dL in men), and polycythemia (>15 g/dL in women, >17 g/dL in men). Differences in group characteristics, one-year readmission, and mortality risk were investigated. Results: In total 1525 subjects with COPD were included at first AECOPD admission in 2018, and divided in anemic, normemic, and polycythemia groups. Prevalence of polycythemia and anemia was 6.8% and 35.2%, respectively. One-year readmission and -mortality risk increased in anemic patients but did not increase in patients with polycythemia. Conclusion: Anemia was predictive of increased risk of one-year readmission and -mortality on patients admitted with AECOPD.