Assessment of calcaemic status in geriatric hospital patients: serum ionized calcium versus albumin-adjusted total calcium.

To evaluate the accuracy of total serum calcium (CaT) and albumin-adjusted total calcium (CaA) determinations in the assessment of calcaemic status in the elderly, serum ionized calcium (CaI), CaT and serum albumin (Alb) concentrations were measured in 558 geriatric hospital patients. As expected, CaT was correlated with Alb (r = 0.316, p less than 0.001) and CaI with serum pH (r = -0.351, p less than 0.001) and they were closely interrelated (r = 0.746, p less than 0.001). Various albumin-adjustment formulas from the literature decreased the correlation of CaT and CaI. Using conventional reference limits for CaT only 12% and 72% of patients with CaI above or below the reference limits for CaI, respectively, were found. This study demonstrates the low sensitivity of total and albumin-adjusted calcium in the detection of slightly or moderately abnormal calcaemic states.