Anaemia of acute inflammation: a higher acute systemic inflammatory response is associated with a larger decrease in blood haemoglobin levels in patients with COVID-19 infection

AIMS: The study tests the hypothesis that a higher acute systemic inflammatory response was associated with a larger decrease in blood hemoglobin levels in patients with Coronavirus 2019 (COVID-19) infection. METHODS: All patients with either suspected or confirmed COVID-19 infection admitted to a busy UK hospital from February 2020 to December 2021 provided data for analysis. The exposure of interest was maximal serum C-reactive protein (CRP) level after COVID-19 during the same admission. RESULTS: A maximal serum CRP >175mg/L was associated with a decrease in blood haemoglobin (-5.0 g/L, 95% confidence interval: -5.9 to -4.2) after adjustment for covariates, including the number of times blood was drawn for analysis.Clinically, for a 55-year-old male patient with a maximum haemoglobin of 150 g/L who was admitted for a 28-day admission, a peak CRP >175 mg/L would be associated with an 11 g/L decrease in blood haemoglobin, compared with only 6 g/L if the maximal CRP was <4 mg/L. CONCLUSIONS: A higher acute systemic inflammatory response is associated with larger decreases in blood haemoglobin levels in patients with COVID-19. This represents an example of anaemia of acute inflammation, and a potential mechanism by which severe disease can increase morbidity and mortality.