Serum calcium as a biomarker of clinical severity and prognosis in patients with coronavirus disease 2019: a retrospective cross-sectional study (preprint)

ABSTRACT

Background: To investigate the correlations between serum calcium and clinical severity and outcomes in patients with coronavirus disease 2019 (COVID-19).Methods: In this clinical retrospective study, the levels of serum calcium, hormone levels and clinical laboratory parameters of admission were recorded. The clinical severity and outcome variables were also recorded.Results: From February 10 to February 28 2020, 241 patients were enrolled in this study. Of these patients, 180 (74.7%) had hypocalcemia on admission. The median serum calcium levels were 2.12 (IQR, 2.04-2.20) mmol/L, median parathyroid hormone (PTH) levels were 55.27 (IQR, 42.73-73.15) pg/mL, median 25-hydroxy-vitamin D (VD) levels were 10.20 (IQR, 8.20-12.65) ng/mL. The serum calcium levels were significantly positive correlated with VD levels (P =0.004), whereas negative correlated with PTH levels (P = 0.048). Patients with lower serum calcium levels (especially ≤2.0 mmol/L) had worse clinical parameters, higher incidence of organ injury septic shock and higher 28-day mortality. The areas under the receiver operating characteristic curves of multiple organ dysfunction syndrome, septic shock, and 28-day mortality were 0.923 (P <0.001), 0.905 (P =0.001), and 0.929 (P <0.001), respectively. The overall mortality of COVID-19 was 4.1% (10/241), whereas the mortality of critical patients was up to 40.0% (10/25). Conclusions: Serum calcium was associated with clinical severity and prognosis of patients with COVID-19. Hypocalcemia may be associated with imbalanced VD and PTH.