Total Calcium Levels in Patients with Hypocalcemia Compared to Ionized Calcium and Adjusted Calcium

Aim: Hypocalcemia is one of the most frequently encountered electrolyte disorders in hospitalized patients. Although laboratories generally measure serum total calcium, the active form of calcium is ionized calcium (iCa). It is necessary to make adjustments considering total calcium values and changes in plasma albumin concentration, based on accurate ionized calcium values. We investigated the relation between hypocalcemia as routinely determined by total calcium measurement, and the gold standard method, ionized calcium measurement, adjusted calcium, and ionized calcium formulas. Material and Methods: 422 patients (Female 43%, Male 57%) with total calcium values lower than 8 mg/dL, and simultaneous ionized calcium, total protein, and albumin results recorded in the automation system of Cebeci Hospital, Faculty of Medicine, Ankara University were evaluated. Adjusted Calcium = Total Calcium + [0.8 × (4.0 – Albumin)] and Ionized Calcium (Zeisler Method) = [(6 × Total Calcium) – (Total Protein × 3)] / (Total Protein + 6) formulas were used. Results: There was no correlation between total calcium, ionized calcium, and calculated ionized calcium results. Correlation coefficient r=0.71 and 95% confidence interval between total calcium and adjusted calcium levels was calculated as 0.6619-0.7545 (p<0.001). Ionized calcium levels in 341 patients (81%) were below 1 mmol/L. Total calcium, ionized calcium, adjusted calcium, and calculated ionized calcium results of only 120 (28.4%) patients suggested hypocalcemia