The influence of hypoxia in predicting COVID-19 mortality in patients with kidney dysfunction on admission in 2 centers in sub-Saharan Africa

Kidney dysfunction (KD) and hypoxia on admission are separately associated with COVID-19 mortality. Estimation of GFR using creatinine and peripheral oxygen saturation (SpO2) may be useful for stratification of at-risk populations. We performed a two centers retrospective cohort study of 359 COVID-19 patients aged 18 years or older to explore the impact of admission kidney function and hypoxia in predicting COVID-19 mortality. KD at admission was defined as estimated glomerular filtration rate (eGFR) calculated by CKD EPI < 60 mL /min/1.73 m2 using creatinine and hypoxia as a SpO2 ˂ 90%. Survival (time-to death) curves were built using the Kaplan–Meier methods. Association between mortality, hypoxia and KD was evaluated by multivariate Cox regression models with a significance level of the p-value set at 0.05. There were 152 patients (42.3%) with an eGFR < 60 mL/min/1.73 m2 and 208 patients (74.8%) with hypoxia on admission. Overall in-hospital mortality was 27.6%, rising to 59.7% in patients with eGFR below 60 mL/min and hypoxia (p < 0.001). Survival was lower in the group of patients with a eGFR below 60 mL/min/1.73 m2 and hypoxia (p < 0.001). Predictors of mortality were eGFR ≥ 60 mL/min/1.73 m2 with hypoxia (HR 2.05 [1.01–4.16], p = 0.048), eGFR < 60 mL/min/1.73 m2 without hypoxia (HR 3.20 [1.73–5.94], p < 0.001) and eGFR < 60 mL/min/1.73 m2 with hypoxia (HR 6.55 [3.63–11.84], p < 0.001). KD on admission and hypoxia are common in COVID-19. Its association with in-hospital mortality should encourage its use in the stratification of patients at risk of death. Influence of hypoxia could suggest a pattern of kidney-lung cross talk.