Measurement of plasma total calcium before plasma free ionized calcium - a possibility with affordable pitfalls.

IF 1.3 4区 医学 Q4 MEDICINE, RESEARCH & EXPERIMENTAL
Tobias Skou Kjøller, Bent S Lind, Peter Schwarz, Henrik L Jørgensen
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引用次数: 0

Abstract

Free ionized calcium (fCa) is considered the gold standard for assessing calcium status in patients, but it is relatively expensive and is associated with several preanalytical and analytical error sources. We investigated the feasibility of using a reflex test that involves first measuring total calcium (tCa) and if out of reference range, then measure fCa, with expectation of reducing the number of fCa measurements. We used data from 1815 unique patients with concurrent measurement of fCa, tCa and albumin adjusted calcium (aCa). Patients were stratified by albumin level, and the association of fCa to tCa and aCa respectively was assessed with linear regression. The regression analysis showed the best linearity for tCa and aCa at albumin <35 g/L (R2: 0.80-0.90), and the poorest at albumin >40 g/L (R2: tCa 0.58; aCa 0.59). We examined the accuracy of hypo- and hypercalcemia classifications for tCa, aCa and the reflex test. aCa had more misclassifications of hypo- and hypercalcemia than tCa, with respectively 25% and 21%. Implementation of the reflex test would correct any false hypo- or hypercalcemia classified by tCa, leaving only false negative results corresponding to 9% of all tCa measurements. False negative results were on average 0.04 mmol/L above or below the reference range of fCa. Implementation of the reflex test reduces the number of fCa by 68% without major errors diagnosing hyper- or hypocalcemia.

先测量血浆总钙,再测量血浆游离离子钙--有可能,也有可能存在负担不起的隐患。
游离离子钙(fCa)被认为是评估患者血钙状况的黄金标准,但其价格相对昂贵,而且与分析前和分析中的一些误差源有关。我们研究了使用反射测试的可行性,即首先测量总钙(tCa),如果超出参考范围,再测量游离钙,从而减少游离钙的测量次数。我们使用了 1815 例同时测量 fCa、tCa 和白蛋白调整钙(aCa)的患者的数据。根据白蛋白水平对患者进行了分层,并通过线性回归评估了 fCa 与 tCa 和 aCa 的关系。回归分析表明,tCa 和 aCa 在白蛋白 R2:0.80-0.90)时,tCa 和 aCa 的线性关系最好,而白蛋白大于 40 g/L 时,线性关系最差(R2:tCa 0.58;aCa 0.59)。我们检查了 tCa、aCa 和反射试验对低钙血症和高钙血症分类的准确性。与 tCa 相比,aCa 对低钙血症和高钙血症分类的误判率更高,分别为 25% 和 21%。采用反射测试可纠正任何由 tCa 分类的错误低钙血症或高钙血症,只留下相当于所有 tCa 测量值 9% 的假阴性结果。假阴性结果平均比 fCa 参考范围高或低 0.04 mmol/L。采用反射测试可将 fCa 的数量减少 68%,而不会出现诊断高钙血症或低钙血症的重大错误。
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来源期刊
CiteScore
3.50
自引率
4.80%
发文量
85
审稿时长
4-8 weeks
期刊介绍: The Scandinavian Journal of Clinical and Laboratory Investigation is an international scientific journal covering clinically oriented biochemical and physiological research. Since the launch of the journal in 1949, it has been a forum for international laboratory medicine, closely related to, and edited by, The Scandinavian Society for Clinical Chemistry. The journal contains peer-reviewed articles, editorials, invited reviews, and short technical notes, as well as several supplements each year. Supplements consist of monographs, and symposium and congress reports covering subjects within clinical chemistry and clinical physiology.
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