A combined role for low vitamin D and low albumin circulating levels as strong predictors of worse outcome in COVID-19 patients

Purpose: We aimed to assess the combined role of vitamin D and albumin serum levels as predictors of COVID-19 disease progression. Methods: We conducted a prospective observational study on adult patients hospitalized for SARS-CoV-2 pneumonia (March-September 2020). Vitamin D and albumin serum levels were measured on admission. These variables were categorized in albumin < 3.5 or ≥ 3.5 g/dL and vitamin D < 30 ng/mL or ≥ 30 ng/mL. We excluded patients with known bone diseases, renal failure, hypercalcemia and/or treated with antiepileptic drugs and steroids, and patients who received previous vitamin D supplementation. A composite outcome including any ventilatory support, PaO2/FiO2 ratio, and 60-day mortality was defined. Results: Sixty-nine patients were enrolled, of whom 50% received non-invasive (NIV) or invasive mechanical ventilation (IMV), 10% died, whereas 89% and 66% presented low albumin and low vitamin D serum levels, respectively. No correlation between vitamin D and albumin levels was found. In multivariable logistic regression analyses adjusted for sex and age-corrected comorbidities, patients having albumin < 3.5 g/dL and vitamin D < 30 ng/mL showed a significant increased risk for all study outcomes, namely NIV/IMV (OR 3.815; 95% CI 1.122-12.966; p = 0.032), NIV/IMV or death (OR 3.173; 95% CI 1.002-10.043; p = 0.049) and PaO2/FIO2 ≤ 100 (OR 3.410; 95% CI 1.138-10.219; p = 0.029). Conclusion: The measurement of both vitamin D and serum albumin levels on COVID-19 patients' admission, and their combined evaluation, provides a simple prognostic tool that could be employed to guide prompt clinical decisions.