Department of Medical Sciences, University of Manchester, Manchester, UK.
Department of Clinical Biochemistry, Manchester Royal Infirmary, 5293Manchester University NHS Foundation Trust, Manchester, UK.
Ann Clin Biochem. 2023 Jan;60(1):54-62. doi: 10.1177/00045632221131673. Epub 2022 Oct 14.
Laboratories are recommended to use patient data to derive their local adjusted calcium (adjCa) equation, using numerous criteria to exclude patients with potential calcium metabolism abnormalities. It is not known which, if any, of the exclusions influence the final equation formula, or to what extent. This study investigated the effect using fewer exclusions has on adjCa equations and on patient results when compared to a reference equation.
A reference ACB adjCa equation was derived from the total calcium and albumin pairs of 1305 individuals who, from an initial 22,906 adults, met recommended criteria (excluding abnormalities in either calcium, albumin, creatinine, magnesium, ALP or ALT, and specific clinical areas). This reference equation was compared to seven alternatives derived using fewer criteria, including one with no exclusions. All equations were applied to a validation cohort (=19,640) to determine their effect on adjCa results and on categorizing patients into hypo-, normo- or hypercalcaemia.
Most alternative adjCa equations, including the one without any exclusions, showed no statistical ( < 0.05) difference in their slope or intercept compared to the ACB reference. Nor did any of the validation cohort have a clinically significantly different adjCa result (>5% and >0.1 mmol/L different) when applying an alternative rather than the reference equation. Additionally, no alternative equation changed the kappa categorization of the validation population's calcium status.
When deriving adjCa equations, most exclusion criteria have little influence on the equation or patient results, including using none at all. This knowledge could simplify deployment of local equations.
实验室建议使用患者数据得出其本地调整钙（adjCa）方程，使用众多标准排除潜在钙代谢异常的患者。目前尚不清楚哪些排除标准会影响最终方程公式，或者影响程度如何。本研究通过使用较少的排除标准，调查了对 adjCa 方程和患者结果的影响，与参考方程进行了比较。
从总钙和白蛋白对 1305 名个体中得出了 ACB adjCa 参考方程，这些个体最初来自 22906 名成年人，符合推荐的标准（排除钙、白蛋白、肌酐、镁、碱性磷酸酶或丙氨酸氨基转移酶以及特定临床领域的异常）。将该参考方程与使用较少标准得出的七种替代方案进行了比较，其中一种方案没有排除标准。所有方程均应用于验证队列（=19640），以确定它们对 adjCa 结果和将患者分类为低钙血症、正常钙血症或高钙血症的影响。
大多数替代 adjCa 方程，包括没有任何排除标准的方程，与 ACB 参考相比，其斜率或截距没有统计学差异（<0.05）。在应用替代方程而不是参考方程时，验证队列中也没有任何一个患者的 adjCa 结果有临床显著差异（>5%和>0.1mmol/L 不同）。此外，没有替代方程改变验证人群钙状态的kappa 分类。
在得出 adjCa 方程时，大多数排除标准对方程或患者结果的影响很小，包括完全不使用排除标准。这一知识可以简化本地方程的部署。
