GSTM1 and anemia (phenotype): Considering that the reported effect of anemia typically elicits a p50 increase of ∼4 mmHg (∼26.7–∼30.7 mmHg; pH 7.4, 37°C), following a ∼50% reduction in [Hb] (resulting from reduced RBC production or loss of RBCs; ∼14.8 g/dL to ∼7.5 g/dL), with compensation provided by increased 2,3 DPG (∼12.7 μmol/gHb to ∼18.7 μmol/gHb) (Boning and Enciso, 1987); the variance in our data and lack of a statistically significant change in p50 might simply reflect the moderate degree of anemia in our COVID-19 population [(Hb) 11.6 ± 2.42 vs 14.1 ± 0.93: g/dL, p = 0.0012; Figure 1E].