Diagnostic performance of predicted ionized calcium in dogs with total hypercalcemia and total hypocalcemia

Abstract

Background: Abnormal total calcium (tCa) values do not necessarily imply dysregulated ionized calcium. Objectives:We aimed to evaluate the diagnostic performance of predicted ionized calcium (piCa) regarding true calcium status in dogs with abnormal tCa. Methods:This was a cross-sectional multicenter study. piCa and its prediction interval (PI) were calculated in 114 dogs, from three different hospitals, with either increased (62) or decreased tCa (52), All dogs also had ionized calcium and a biochemical profile available. The sensitivity, specificity, predictive values, and diagnostic discordance of piCa to confirm ionized hypercalcemia (iHyperCa) and ionized hypocalcemia (iHypoCa) were calculated using logistic regression analysis.Results: iHyperCa was found in 28% and 66% of hyperphosphatemic and nonhyperphosphatemic dogs with tCa above the reference interval upper limit, respectively. The piCa correctly classified dogs with iHyperCa in 72.2% of those with hyperphosphatemia and 93.2% of those without hyperphosphatemia. Comparatively, elevating the tCa threshold to 12 mg/dL properly classified dogs 50% and 75% of the time in hyperphosphatemic and non-hyperphosphatemic dogs, respectively. iHypoCa was found in only 31/52 (60%) dogs with decreased tCa. The piCa correctly classified 55.2 to 100% of dogs with iHypoCa depending on the hospital. The PI demonstrated high sensitivity for iHyperCa (100%) and high specificity for both iHyperCa (100%) and iHypoCa (100%).Conclusions: Evaluating tCa alone does not reliably determine ionized calcium status. Even with hyperphosphatemia, piCa and its PI represent a reliable alternative to interpret abnormal tCa values when ionized calcium measurements are not available.However, if the tCa reference interval is notably different from 7.6 to 11.4 mg/dL, piCa values might be under/overestimated.

Association between total hypercalcaemia and iliosacral lymph node metastasis in dogs diagnosed with anal sac adenocarcinoma using abdominal ultrasonography

“…In that study, the discordance between hypercalcaemia classified by total versus ionized calcium in non-hyperphosphataemic patients was 34.1% (Lebastard et al, 2021). Therefore, the current study could have underestimated or overestimated the number of dogs that were truly hypercalcaemic.…”

“…It has been previously reported that using total calcium to predict elevated ionized calcium may lead to an overestimation of normocalcaemia (Schenck & Chew, 2005). However, a more recent study demonstrated that total calcium may lead to an overestimation of elevated ionized calcium (Lebastard et al, 2021).…”

“…It has been previously reported that using total calcium to predict elevated ionized calcium may lead to an overestimation of normocalcaemia (Schenck & Chew, 2005 ). However, a more recent study demonstrated that total calcium may lead to an overestimation of elevated ionized calcium (Lebastard et al., 2021 ). In that study, the discordance between hypercalcaemia classified by total versus ionized calcium in non‐hyperphosphataemic patients was 34.1% (Lebastard et al., 2021 ).…”

“…However, a more recent study demonstrated that total calcium may lead to an overestimation of elevated ionized calcium (Lebastard et al., 2021 ). In that study, the discordance between hypercalcaemia classified by total versus ionized calcium in non‐hyperphosphataemic patients was 34.1% (Lebastard et al., 2021 ). Therefore, the current study could have underestimated or overestimated the number of dogs that were truly hypercalcaemic.…”

Plasma Ionized Calcium and Magnesium Concentrations and Prevalence of Subclinical Hypocalcemia and Hypomagnesemia in Postpartum Grazing Holstein Cows from Southern Chile

“…Therefore, these authors recommend the evaluation of iCa in plasma as a more accurate predictor of blood Ca status in dairy cattle. In addition, in other species such as dogs (Lebastard et al, 2021) and humans (Papadopoulou et al, 2021;Yu and Sharma 2022), the evaluation of calcemia to establish proper treatment strategies in patients under hospital settings is consistently centered on iCa instead of tCa. Nevertheless, most studies dealing with hypocalcemia in dairy cattle report tCa concentrations, possibly due to the complexity of blood sample processing and the higher cost of laboratory analysis for iCa.…”