Admission calcium levels and risk of acute kidney injury in hospitalised patients

Background: The risk of acute kidney injury (AKI) development among hospitalised patients with elevated calcium levels on admission remains unclear. The aim of this study was to assess the risk of AKI in hospitalised patients stratified by various admission serum calcium levels. Methods: This is a single-centre retrospective study conducted at a tertiary referral hospital. All hospitalised adult patients who had admission calcium levels available between 2009 and 2013 were enrolled. Admission calcium was categorised based on its distribution into six groups (≤7.9, 8.0-8.4, 8.5-8.9, 9.0-9.4, 9.5-9.9, and ≥10.0 mg/dL). The primary outcome was hospital-acquired AKI. Logistic regression analysis was performed to obtain the odds ratio of AKI for various admission calcium strata using calcium levels of 8.0-8.4 mg/dL (lowest incidence of AKI) as the reference group. Results: A total of 12 784 patients were studied. Hospital-acquired AKI occurred in 1779 (13.9%) patients. The incidence of AKI among patients with admission calcium ≤7.9, 8.0-8.4, 8.5-8.9, 9.0-9.4, 9.5-9.9 and ≥10 mg/dL was 14.7%, 11.7%, 11.8%, 14.6%, 15.8% and 17.3%, respectively. After adjusting for potential confounders, admission calcium levels ≤7.9, 9.0-9.4, 9.5-9.9 and ≥10 mg/dL were associated with increased risk of AKI with odds ratios of 1.36 (95%CI 1.08-1.72), 1.29 (95%CI 1.08-1.56), 1.38 (95%CI 1.14-1.68) and 1.51 (95%CI 1.19-1.91), respectively. Conclusion: Admission hypocalcaemia and hypercalcaemia are associated with an increased risk for hospital acquired AKI. Patients with admission hypercalcaemia (≥10 mg/dL) carry a 1.51-fold risk for AKI development during hospitalisation.