New Predictive Equations for Serum Ionized Calcium in Hospitalized Patients

Abstract

Objective: To study a new and easy way to calculate equations to predict ionized calcium (Ca²⁺) for adult hospitalized patients with the usual laboratory and clinical parameters. Subjects and Methods: This retrospective observational study was conducted in a third-level university hospital. An initial learning cohort (cohort L: 269 patients) was selected to derive the new equations. These equations were tested in a validation of another cohort (cohort V: 146 patients). Patients selected were hospitalized adults who had simultaneous determinations of Ca²⁺ and serum total calcium (CaTot). They were classified using their estimated glomerular filtration rate (GFRe) into normal function, moderate and severe kidney dysfunction. Demographic and biochemical parameters, in addition to comorbidities, were collected from hospital databases. Nine published equations to predict Ca²⁺ and 2 widely used equations to predict corrected CaTot were also selected to be compared to newer equations for accuracy in detecting serum calcium alterations. New equations were derived by a multiple linear-regression analysis from patients in cohort L. Results: Three equations were derived containing the CaTot square root as the main independent variable. Equation 1: Ca²⁺ = 0.815 × CaTot^0.5. Equation 2: Ca²⁺ = 0.826 × CaTot^0.5 - 0.023 × renal function. Equation 3: Ca²⁺ = 0.813 × CaTot^0.5 - 0.006 × albumin^0.75 + 0.079. These equations performed better than published equations to predict Ca²⁺ when their error measures were analyzed in cohort V, even in special populations such as critically ill and very old patients. Conclusions: Three new equations predicting Ca²⁺ were derived requiring easily available clinical and laboratory parameters. They could be valuable in predicting hypocalcemia but are of limited use in hypercalcemia.

Effects of pH and the plasma or serum concentrations of total calcium, chloride, magnesium,l‐lactate, and albumin on the plasma ionized calcium concentration in calves

“…Nevertheless, the in vivo effect of a 10 mmol/L increase in c Cl approximates that induced by a 0.2 unit decrease in pH, suggesting that it is inappropriate to focus corrective equations for c Ca 2+ only on changes in pH unless the sample was not collected and stored in an anaerobic manner. Although calculation of c Ca 2+ from 5 predictors produced a value with a 95% CI of 10%, our findings provide a potential explanation for why “corrective” equations that include pH and plasma c Albumin or c Total protein but exclude c Cl are poorly predictive of c Ca 2+ in human plasma, canine plasma, and bovine serum . Our findings also were consistent with a recent study in dogs that indicated serum c Cl was an important predictor of whole‐blood c Ca 2+ .…”

The Effect of Pre-Thyroidectomy Calcitriol Prophylaxis on Post-Thyroidectomy Hypocalcaemia in Children

“…Albumin was measured using the bromcresol green method on subsequent analytical platforms (Hitachi 747, Modular, Cobas 8000) from Roche Diagnostics. Total calcium concentration was calculated using the formula CaTot 0.5 = ([0.006 × Alb 0.75 ] − 0.079 + Ca 2+ )/0.813 [ 9 ]. We used sets of ionized and total calcium of patients who had both measurements performed at our clinical chemistry laboratory, to test the usefulness of this formula for our patient group.…”

Serum sodium variation is a major determinant of peridialytic blood pressure trends in haemodialysis outpatients

“…Serum albumin was determined by the bromocresol green method. Total serum calcium was measured and ionized calcium calculated using the Mateu-de Antonio equation, derived from patients with kidney failure (0.815 × total calcium 0.5 ) 11 . Bioelectrical impedance analysis was performed prior to and 20–30 min after the HD session using multifrequency segmental InBody 720 Body Composition Analysis (Biospace, Seoul, South Korea), following a standardized protocol 12 .…”