Admission Electrolyte Abnormalities and Clinical Outcomes in Hospitalized COVID-19 Patients

Background and Objectives: Electrolyte abnormalities are frequently observed in hospitalized patients with acute infections and may reflect underlying disease severity. This study aimed to investigate the association between baseline electrolyte disturbances and clinical outcomes in patients with COVID-19, with a particular focus on albumin-corrected calcium levels. Materials and Methods: This retrospective study included 348 hospitalized patients with COVID-19. Primary analyses were restricted to RT-PCR-confirmed cases (n = 272) to minimize misclassification bias, while the full cohort was evaluated in sensitivity analyses. Baseline electrolyte levels at admission were recorded, and corrected calcium levels were calculated using serum albumin. Clinical outcomes included prolonged hospitalization (defined relative to the cohort median), intensive care unit (ICU) admission, invasive mechanical ventilation (IMV), and in-hospital mortality. Multivariable logistic regression analyses were performed adjusting for age, sex, and renal function (eGFR). Results: In the PCR-confirmed cohort, corrected hypocalcemia was present in 37.3% of patients. In univariate analyses, hypocalcemia, hyponatremia, and hypophosphatemia were significantly associated with adverse outcomes. However, after adjustment, corrected hypocalcemia did not retain independent significance. Hyponatremia remained independently associated with ICU admission (OR: 9.45, 95% CI: 2.12–42.1, p = 0.003), while hypophosphatemia was independently associated with prolonged hospitalization (OR: 2.83, 95% CI: 1.36–5.91, p = 0.005). No electrolyte abnormality demonstrated a stable independent association with IMV requirement or mortality after adjustment. Sensitivity analyses in the full cohort yielded consistent findings. Conclusions: Electrolyte abnormalities are common in hospitalized COVID-19 patients and are associated with worse clinical outcomes; however, they primarily reflect overall disease severity rather than acting as independent prognostic determinants. Routine electrolyte measurements may provide accessible and clinically informative markers but should be interpreted in conjunction with other clinical parameters.