Anemia during SARS-CoV-2 infection is associated with rehospitalization after viral clearance

Patients with COVID-19 can experience symptoms and complications after viral clearance. It is important to identify clinical features of patients who are likely to experience these prolonged effects. We conducted a retrospective study to compare longitudinal laboratory test measurements (hemoglobin, hematocrit, estimated glomerular filtration rate, serum creatinine, and blood urea nitrogen) in patients rehospitalized after PCR-confirmed SARS-CoV-2 clearance (n = 104) versus patients not rehospitalized after viral clearance (n = 278). Rehospitalized patients had lower median hemoglobin levels in the year prior to COVID-19 diagnosis (Cohen's D = -0.50; p = 1.2 × 10^-3) and during their active SARS-CoV-2 infection (Cohen's D = -0.71; p = 4.6 × 10^-8). Rehospitalized patients were also more likely to be diagnosed with moderate or severe anemia during their active infection (Odds Ratio = 4.07; p = 4.99 × 10^-9). These findings suggest that anemia-related laboratory tests should be considered in risk stratification algorithms for patients with COVID-19.