A number of COVID-19 patients with rare anemias, including aplastic anemia,16 sickle cell anemia,17 thalassemia,18 autoimmune hemolytic anemia,19 and megaloblastic anemia,20 have been recently reported. However, little proportion of attention was paid on common anemia in COVID-19 patients. Our data demonstrated that approximately 44.5% of COVID-19 patients were proved to have anemia (common) and the proportions were dramatically higher than that of other underlying diseases, such as hypertension, diabetes, cardiovascular disease and malignant tumor.11, 21 In this study, we firstly presented clinical characteristics and laboratory results of COVID-19 patients with anemia in a large amount (137 cases) and meanwhile investigating the impact of anemia on COVID-19.
After comparison of the symptoms between anemic COVID-19 patients and the counterparts without anemia, the results showed that anemic patients less likely to develop fever and cough in the early stage of COVID-19, indicating the concealment of COVID-19 patients with anemia. Fever has been extensively utilized as an indicator to screen suspected COVID-19 patients at public places, such as airports, mall and cinemas, and it has been proved effectively.
Therefore, the COVID-19 patients with anemia may be easily to evade the screening and brings a huge challenge to the control and management of this epidemic.
Meanwhile, COVID-19 patients with anemia are more likely to have decreased interleukin-6 (IL-6), which indicates severe inflammatory reaction.22 Additionally, previous study has proved the association of elevated serum levels of IL-6 with progress of COVID-19.11 These results suggest that anemic patients possess a high possibility to develop severe pneumonia. Consistently, comparison of the severe COVID-19 patients in anemia group and non-anemia group revealed that 27.9% of the anemic patients ultimately developed severe pneumonia, significantly higher than that of patients without anemia. Moreover, the anemia was identified as an independent risk factor of the severe and critical COVID-19, as evidenced by analyses of multivariable logistic regression. The related OR value demonstrates that COVID-19 patients with anemia are more likely to develop severe pneumonia, with the possibility of 8.2 times higher than that having no anemia. Severe COVID-19 generally accompanies the low oxygen levels of arterial blood, and for instance, a vital criterion of identifying severe pneumonia was to determine whether the blood oxygen saturation was below 93% when rest. In anemia patients, the insufficient hemoglobin impaired the oxygenation capability of blood and exacerbated the anoxia in multiply organs and tissues, thus leading to aggravation of pneumonia. In addition, the enhanced inflammation reaction, as evidenced by elevated levels of IL-6, in anemic patients was speculated to be yet contributed to the progress of COVID-19.
This work firstly presents a large retrospective cohort study among COVID-19 patients with anemia and proves the association of anemia with severe pneumonia. Therefore, the thorough evaluation of anemia is recommended in COVID-19 patients when diagnosis. Timely treating anemia and increasing the hemoglobin levels are important in controlling the progress of pneumonia.