Abstract
The serum total calcium (tCa) level is used for blood Ca evaluations, but it is difficult to assess in patients with hypoproteinemia. Since the physiological effects of Ca are determined by ionized Ca (iCa), iCa should be measured rather than tCa. The serum Ca target range for dialysis (HD) patients is 8.4-10.0 mg/dL, but the target range for iCa has not been determined. Gas analysis (GAS) was performed using the RAPIDLab1200 (SIEMENS) in 37 HD patients during routine examinations. Furthermore, frozen serum samples from the same patients were sent to a commercial company to have their iCa and pH levels measured. Serum albumin (Alb) levels were measured using the modified bromocresol purple method. In cases involving Alb levels of ≤3.1 g/dL and ≥4.0 g/dL, Alb-corrected Ca levels were calculated using the KDOQI-1 and KDOQI-2 formulas, respectively. Relationships were detected between GAS-derived pH-corrected iCa levels and Alb-corrected Ca levels (y=0.092x + 0.300, r=0.807) and between outsourced serum test-derived pH-corrected iCa levels and in-hospital serum test-derived Alb-corrected Ca levels (y=0.132x+0.092, r=0.853). A Ca target range of 8.4-10.0 mg/dL corresponds to iCa ranges of 1.07-1.22 mmol/L and 1.20-1.41 mmol/L when the GAS and outsourcing methods are used, respectively.
