In contrast, Daniel et al. [21] observed that the in vitro Hb-O2 affinity in 14 patients affected by COVID-19 did not differ from that of 11 control patients in standard conditions; similarly, Pascual-Guardia et al. [22] did not find any change in the Hb-O2 affinity in COVID-19 patients. The gene discussed is GSTM1; the disease is COVID-19.