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Updated: Sep 24, 2025
A Semi-Automated and Reproducible Biological-Based Method to Quantify Calcium Deposition In Vitro
Published on: June 2, 2022
Novel methods of predicting ionized calcium status from routine data in critical care: External validation in
Ernie Yap1, Jie Ouyang1, Isha Puri1
1Department of Medicine, Downstate Medical Center, State University of New York, 450 Clarkson Ave., Brooklyn, NY, USA.
Insights
New models, Pred-ICa and ProbHYPO, accurately predict ionized calcium (ICa) levels in critical care patients. These models improve upon traditional methods for detecting low ICa, aiding clinical decisions.
Area of Science:
- Critical care medicine
- Clinical chemistry
- Biomarker validation
Background:
- Low ionized calcium (ICa) is common in critical care but difficult to detect using total calcium (TCa) or albumin-corrected TCa (cTCa).
- Novel models (Pred-ICa, ProbHYPO) were developed to estimate ICa by adjusting TCa for albumin and anion gap components.
- Previous models showed promise in internal validation but required external validation.
Purpose of the Study:
- To externally validate four new anion gap-based models for predicting ionized calcium (ICa).
- To assess the diagnostic accuracy of these models in identifying low and high ICa in critically ill patients.
- To compare the performance of new models against albumin-corrected total calcium (cTCa).
Main Methods:
- Utilized the Medical Information Mart for Intensive Care III (MIMIC-III) database.
- Included 4105 patients with paired arterial blood gas and chemistry panel measurements.
- Evaluated four models and cTCa for diagnostic discrimination and agreement with measured ICa.
Main Results:
- The Pred-ICa and ProbHYPO models demonstrated superior diagnostic discrimination and agreement.
- These models outperformed cTCa in identifying abnormal ICa levels.
- External validation in the MIMIC-III cohort confirmed the efficacy of Pred-ICa and ProbHYPO.
Conclusions:
- Pred-ICa and ProbHYPO models are externally validated and effective for predicting ionized calcium in critical care.
- These models offer a more efficient approach to determining the need for direct ICa testing.
- Clinical utility is enhanced by improved accuracy in assessing ICa status.
Background:
Low ionized calcium (ICa) is prevalent and prognostic in critical care, but poorly detected by either total calcium (TCa) or albumin-corrected TCa (cTCa). We recently derived models of ICa (Pred-ICa) and low ICa (ProbHYPO) in critical care that adjust TCa for binding to albumin and small anions-represented by the anion gap's components. On internal validation, they outperformed cTCa in diagnosing low ICa. Two other new anion gap-based models of ICa, derived in renal patients, have not been validated. This study tested the external validity of these 4 new models in the Medical Information Mart for Intensive Care III (MIMIC-III) database.
Methods:
We identified 4105 patients in MIMIC-III with ICa measured on an arterial blood gas panel within 20 min of chemistry panel measurements of TCa, albumin, sodium, chloride, and total carbon dioxide. The 4 models and cTCa were assessed by their diagnostic discrimination for low ICa (<1.10 mmol/l) and high ICa (>1.32 mmol/l), and by the agreement between predicted and observed values.
Results:
Pred-ICa and ProbHYPO had the best discrimination and agreement.
Conclusions:
Pred-ICa and ProbHYPO were externally validated in MIMIC-III. They can help clinicians efficiently decide when to order direct ICa testing in critical care.
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