Albumin-adjusted calcium is not suitable for diagnosis of hyper- and hypocalcemia in the critically ill

Abstract

Objective: To evaluate whether calcium adjusted for albumin can be used to monitor calcium homeostasis in critically ill patients.

Design: Prospective single-single center observational study.

Setting: Clinical laboratory and critical care unit of a regional teaching hospital.

Patients: Fifty-three paired samples were from 36 patients requiring intensive care treatment.

Interventions: None.

Measurements and main results: Total calcium, albumin-adjusted calcium, and ionized calcium were measured in critically ill patients during an 8-wk period. Calcium was adjusted for albumin using the formula that is most frequently used in The Netherlands. Using ionized calcium as the gold standard, albumin-adjusted calcium overestimated hypercalcemia and totally missed hypocalcemia. The same seemed to be true for other formulas used for albumin or protein adjustment of calcium concentrations.

Conclusions: Albumin-adjusted calcium cannot be used in an intensive care setting to monitor reliably the calcium levels in critically ill patients and should be replaced by measurement of ionized calcium.