The Affinity of Hemoglobin for Oxygen Is Not Altered During COVID-19

Abstract

Background: A computational proteomic analysis suggested that SARS-CoV-2 might bind to hemoglobin (Hb). The authors hypothesized that this phenomenon could result in a decreased oxygen (O2) binding and lead to hemolytic anemia as well. The aim of this work was to investigate whether the affinity of Hb for O2 was altered during COVID-19.Methods: In this retrospective, observational, single-center study, the blood gas analyses of 100 COVID-19 patients were compared to those of 100 non-COVID-19 patients. Fifty-five patients with carboxyhemoglobin (HbCO) ≥8% and 30 with sickle cell disease (SCD) were also included (“positive controls” with abnormal Hb affinity). P50 was corrected for body temperature, pH, and PCO2.Results: Patients did not differ statistically for age or sex ratio in COVID-19 and non-COVID-19 groups. Median P50 at baseline was 26 mmHg [25.2–26.8] vs. 25.9 mmHg [24–27.3], respectively (p = 0.42). As expected, P50 was 22.5 mmHg [21.6–23.8] in the high HbCO group and 29.3 mmHg [27–31.5] in the SCD group (p < 0.0001). Whatever the disease severity, samples from COVID-19 to non-COVID-19 groups were distributed on the standard O2-Hb dissociation curve. When considering the time-course of P50 between days 1 and 18 in both groups, no significant difference was observed. Median Hb concentration at baseline was 14 g.dl–1 [12.6–15.2] in the COVID-19 group vs. 13.2 g.dl–1 [11.4–14.7] in the non-COVID-19 group (p = 0.006). Among the 24 COVID-19 patients displaying anemia, none of them exhibited obvious biological hemolysis.Conclusion: There was no biological argument to support the hypothesis that SARS-CoV-2 could alter O2 binding to Hb.

The oxygen dissociation curve of blood in COVID-19

“…Recently, an article was published stating that there is no effect of COVID-19 on the oxygen dissociation curve ( 81 ). However, in this study only nonsevere cases mostly without anemia were investigated.…”

The Impact of COVID-19 Infection on Oxygen Homeostasis: A Molecular Perspective

“…The time-course of P50 between days 1 and 18, showed no significant differences among the groups. Median P50 at baseline was 26 mmHg (25.2-26.8) vs. 25.9 mmHg (24-27.3), respectively (Gille et al, 2021).…”

Reply to Gille et al.

“…to the editor: We thank Dr. Gille and collaborators for their comment ( 1 ) to our review ( 2 ). The following statements in their letter have to be discussed: 1 ) In contrast to the findings of Vogel et al ( 3 ), the in vivo oxygen dissociation curve is not left-shifted in the patients of their recent study ( 4 ). 2 ) There is no marked increase in methemoglobin concentration in their patients as suggested by us for Vogel’s results.…”

“…The number of measurements is much smaller in Gille’s than in Vogel’s investigation [19,463 from 43 patients with COVID-19 and 828 critically ill patients with acute respiratory failure ( 3 )]. Gille et al ( 4 ) evaluated 474 samples from 100 patients with COVID-19 and 100 subjects with other respiratory problems. In addition to the affinity difference between the patient groups, a significant decrease of P 50 relative to the standard value calculated according to Severinghaus ( 5 , 6 ) was found in the subjects infected with SARS-CoV-2 by Vogel et al ( 3 ).…”