Hypo- and Hyperphosphatemia at Admission as Independent Factors of Mortality of COVID-19 Patients: Findings from a Retrospective Cohort Study

Background: Electrolyte imbalances are common in COVID-19 infection and are associated with poor outcomes in hospitalized patients. Objectives: This study examined whether serum phosphate imbalances at admission are associated with mortality in hospitalized COVID-19 patients. Methods: In this registry-based single-center retrospective cohort study, 1349 inpatients with COVID-19 were included from March 2020 to March 2021 in an academic hospital in Ilam (southwest Iran). The Cox proportional hazard (PH) regression model was applied to the data set of COVID-19. Results: The in-hospital median survival time for patients with low, normal, and high serum phosphate levels was 14, 25, and 8 days, respectively. In a multivariate model, adjusted for the other variables, patients with hypophosphatemia (adjusted hazard ratio [HR], 2.53; 95% CI, 1.15 - 5.58; P = 0.02) and hyperphosphatemia (adjusted HR, 1.77; 95% CI, 1.00 - 3.14; P = 0.05) had an increased mortality hazard compared with those who had normal levels of serum phosphate. Conclusions: Our results demonstrate associations of hypophosphatemia and hyperphosphatemia with increased in-hospital mortality in COVID-19 patients. Intensive medical care and more attention must be paid to COVID-19 patients with serum phosphate imbalances at admission.