Internal Medicine Unit, CHV Fregis, Arcueil, France.
Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Canada.
Vet Clin Pathol. 2020 Mar;49(1):48-58. doi: 10.1111/vcp.12835. Epub 2020 Mar 25.
Predicted ionized calcium (piCa) can be calculated from routine biochemistry variables using a recently developed predictive model in dogs. However, it has not been evaluated with variables measured from multiple laboratories.
We aimed to (a) externally validate piCa in dogs where biochemistry results were obtained from different analyzers, and (b) compare the diagnostic performances of piCa and total calcium (tCa).
A cross-sectional multicentric study on 138 dogs from three different hospitals was performed. The sensitivity (Sen), specificity (Spe), positive (PPV) and negative predictive values (NPV), and diagnostic discordance of piCa and tCa were calculated using logistic regression for ionized hypercalcemia and hypocalcemia. Diagnostic performance fluctuations across hospitals were also assessed.
For ionized hypercalcemia, the Sen (81.8%), Spe (96.1%), PPV (69.2%), NPV (97.7%), and diagnostic discordance (5.1%) of piCa were not significantly different among hospitals or from those of tCa. For ionized hypocalcemia, the Sen (range: 9.7%-53.8%) and Spe (range: 95.6%-99.6%) of piCa and tCa (Sen range: 16.2%-87.8%; Spe range: 58.3%-98.1%) varied across hospitals, although to a lesser extent for piCa. The diagnostic discordances of piCa (20.3%) and tCa (25.4%) were close. The prediction interval (PI) of piCa demonstrated high Sen to screen for ionized hypercalcemia (100%) and hypocalcemia (range: 75%-93.3%), and high Spe to diagnose ionized hypercalcemia and hypocalcemia (100% for both).
These results support the external validation of piCa in dogs. Its PI represents a notable advantage over tCa to help clinicians explore calcium-related disorders when ionized calcium cannot be readily measured.
预测离子钙（piCa）可通过最近开发的犬预测模型，从常规生化变量中计算得出。然而，它尚未通过来自多个实验室测量的变量进行评估。
我们旨在（a）在来自不同分析仪的生化结果的犬中外部验证 piCa，以及（b）比较 piCa 和总钙（tCa）的诊断性能。
在来自三个不同医院的 138 只犬中进行了一项跨中心的横断面研究。使用逻辑回归计算 piCa 和 tCa 的离子性高钙血症和低钙血症的灵敏度（Sen）、特异性（Spe）、阳性预测值（PPV）和阴性预测值（NPV）以及诊断不一致性。还评估了医院之间的诊断性能波动。
对于离子性高钙血症，piCa 的 Sen（81.8%）、Spe（96.1%）、PPV（69.2%）、NPV（97.7%）和诊断不一致性（5.1%）在医院之间没有显著差异，与 tCa 也没有显著差异。对于离子性低钙血症，piCa 和 tCa 的 Sen（范围：9.7%-53.8%）和 Spe（范围：95.6%-99.6%）在医院之间存在差异，尽管 piCa 的差异较小。piCa（20.3%）和 tCa（25.4%）的诊断不一致性接近。piCa 的预测区间（PI）对筛查离子性高钙血症（100%）和低钙血症（范围：75%-93.3%）具有高 Sen，对诊断离子性高钙血症和低钙血症具有高 Spe（均为 100%）。
这些结果支持在犬中对 piCa 的外部验证。其 PI 在帮助临床医生在无法直接测量离子钙时探索钙相关疾病方面具有显著优势，优于 tCa。
