Ohbal Takashi, Shiraishi Takeko, Kabaya Takashi, Watanabe Shinichiro
Rinsho Byori. 2014 Feb;62(2):133-8.
The ionized or free fraction of serum calcium is physiologically important for cellular function, but we most often measure total serum calcium. There are a number of correction formulas that can be used to estimate whether low total serum calcium can be attributed simply to low albumin or serum protein. In Japan, Payne's formula has been widely used to correct calcium concentration. However, there are some problems in the measurement methods of total calcium and serum albumin which were used to establish Payne's formula with respect to specificity, calibration curve and stability. Recently, improved measurement methods of calcium and albumin have been adopted at clinical laboratories. Here we evaluated Payne's formula by comparing it with improved measurement methods of total calcium and serum albumin. For the total calcium measurement, o-CPC (o-cresolphthaleincomplexone), CPZ(chlorophosphonazo) III, and enzymatic methods were used. For the serum albumin measurement, BCG (bromocresol green) and improved BCP(bromocresol purple) methods were used. The results of this comparison study suggest that the calcium correction equation is not affected by changes in total calcium concentration, but the assay used for albumin may affect the calcium correction equation. Using multiple linear regression, the following equations were derived: BCG between CPZ III [corrected Ca(mg/dL) = total Ca-0.76ALB + 3.2], and improved BCP between CPZ III [corrected Ca = total Ca-0.7ALB + 2.6]. These formulas are simplified respectively as [corrected Ca = total Ca + 0.8(4-ALB], and [corrected Ca = total Ca + 0.7 (4-ALB)]. We conclude that Payne's formula is valid with the BCG method, but with the improved BCP method, our formula is more suitable for correcting calcium.
血清钙的离子化或游离部分对细胞功能具有重要生理意义，但我们通常测量的是血清总钙。有多种校正公式可用于估计血清总钙降低是否仅归因于白蛋白或血清蛋白水平降低。在日本，佩恩公式已被广泛用于校正钙浓度。然而，用于建立佩恩公式的总钙和血清白蛋白测量方法在特异性、校准曲线和稳定性方面存在一些问题。最近，临床实验室采用了改进的钙和白蛋白测量方法。在此，我们通过将佩恩公式与改进的总钙和血清白蛋白测量方法进行比较来评估该公式。对于总钙测量，使用了邻甲酚酞络合酮（o-CPC）、氯膦酸偶氮胂（CPZ）III和酶法。对于血清白蛋白测量，使用了溴甲酚绿（BCG）和改进的溴甲酚紫（BCP）方法。这项比较研究的结果表明，钙校正方程不受总钙浓度变化的影响，但用于白蛋白检测的方法可能会影响钙校正方程。通过多元线性回归，得出以下方程：CPZ III法中BCG法对应的[校正钙（mg/dL）=总钙 - 0.76×白蛋白 + 3.2]，以及CPZ III法中改进的BCP法对应的[校正钙 = 总钙 - 0.7×白蛋白 + 2.6]。这些公式可分别简化为[校正钙 = 总钙 + 0.8×(4 - 白蛋白)]和[校正钙 = 总钙 + 0.7×(4 - 白蛋白)]。我们得出结论，佩恩公式在BCG法中是有效的，但在改进的BCP法中，我们推导的公式更适合校正钙。
