Anemia in patients with Covid-19: pathogenesis and clinical significance

Abstract

COVID-19 patients typically present with lower airway disease, although involvement of other organ systems is usually the rule. Hematological manifestations such as thrombocytopenia and reduced lymphocyte and eosinophil numbers are highly prevalent in COVID-19 and have prognostic significance. Few data, however, are available about the prevalence and significance of anemia in COVID-19. In an observational study, we investigated the prevalence, pathogenesis and clinical significance of anemia among 206 patients with COVID-19 at the time of their hospitalization in an Internal Medicine unit. The prevalence of anemia was 61% in COVID-19, compared with 45% in a control group of 71 patients with clinical and laboratory findings suggestive of COVID-19, but nasopharyngeal swab tests negative for SARS-CoV-2 RNA (p = 0.022). Mortality was higher in SARS-CoV-2 positive patients. In COVID-19, females had lower hemoglobin concentration than males and a higher prevalence of moderate/severe anemia (25% versus 13%, p = 0.032). In most cases, anemia was mild and due to inflammation, sometimes associated with iron and/or vitamin deficiencies. Determinants of hemoglobin concentration included: erythrocyte sedimentation rate, serum cholinesterase, ferritin and protein concentrations and number of chronic diseases affecting each patient. Hemoglobin concentration was not related to overall survival that was, on the contrary, influenced by red blood cell distribution width, age, lactate dehydrogenase and the ratio of arterial partial oxygen pressure to inspired oxygen fraction. In conclusion, our results highlight anemia as a common manifestation in COVID-19. Although anemia does not directly influence mortality, it usually affects elderly, frail patients and can negatively influence their quality of life.

Keywords: Anemia; Anemia of inflammation; COVID-19; Oxygen partial pressure/oxygen concentration; Red blood cell distribution width.

Fig. 1

Kaplan–Meier survival curves of (a) SARS-CoV-2 positive (red line) and control SARS-CoV-2 negative (blue line) patients and (b) of anemic (red line) and non-anemic (blue line) SARS-CoV-2 positive patients. The difference between SARS-CoV-2 positive and SARS-CoV-2 negative patients is significant (p = 0.033)

Fig. 2

Causes of anemia in 126 anemic patients with laboratory-confirmed COVID-19. Serum concentrations of vitamin B₁₂ and folate were available only for a subset of patients (N = 57); the prevalence of vitamin deficiencies can, therefore, be underestimated