A comparison of corrected serum calcium levels to ionized calcium levels in haemodialysis patients

Aberrations in calcium homeostasis are common observed in patients with chronic renal failure. Measure of total calcium does not reflect the real variation of the calcium status. The proper method to evaluate this issue in hemodialysis patients has not been completely defined. This study aimed to compare the corrected serum calcium levels to ionized calcium levels in hemodialysis patients. Thirty one patients on chronic haemodialysis admitted at the hemodialysis department were retrospectively reviewed. Calcium status was evaluated by measure of ionized levels and as a function of serum calcium levels corrected for albumin aberrations. Based on the measurement of ionized calcium and total calcium corrected, patients were classified into three categories: hypocalcemic, normocalcemic and hypercalcemic. Our result showed that the corrected serum calcium values failed to accurately classify calcium status in 41% of cases. The sensitivity and specificity of the corrected serum calcium formula to evaluate hypocalcemia were 53% and 85%, respectively. Corrected serum values underestimated the prevalence of hypocalcemia and overestimated the prevalence of normocalcemia. In total, the results obtained allow to conclude the lack of interest in the use of correction formulas. Calcium homeostasis should be evaluated by ionized calcium levels rather than as a function of serum calcium and albumin.