2018 Volume 51 Issue 1 Pages 103-107
The biological effects of calcium are determined by the ionized calcium concentration (iCa). However, since the iCa is not routinely measured in many guidelines evaluations of Ca concentrations are based on the total calcium concentration (tCa). The tCa accurately reflects the iCa in patients with normal albumin levels, but not in patients with hypoalbuminemia. The guidelines produced by the Japanese Society for Dialysis Therapy recommend correcting the tCa using Payne’s formula: corrected Ca=tCa+(4−albumin). The iCa, tCa, and serum albumin level were measured simultaneously just before the first dialysis session of the week. Among the 41 hemodialysis patients investigated, 33 had hypoalbuminemia (a serum albumin level of<3.7 g/dL) and were included in the analysis. Payne’s formula and two formulae recommended by the Kidney Disease Outcomes Quality Initiative (KDOQI; the KDOQI-1 and KDOQI-2 formulae) were used to estimate the iCa. The serum albumin level was measured using the modified bromocresol purple method. The measured albumin levels were converted using the conventional bromocresol green method by adding 0.3 mg/dL. The KDOQI-1 formula exhibited the highest specificity for predicting the iCa (R2: 0.50), followed by the tCa (R2: 0.45), the KDOQI-2 formula (R2: 0.44), and Payne's formula (R2: 0.37) in the 33 hemodialysis patients with hypoalbuminemia. In conclusion, this study suggested that the KDOQI-1 formula might be useful for predicting the iCa in hemodialysis patients with hypoalbuminemia.
