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Published on: June 2, 2022
Approximation of Corrected Calcium Concentrations in Advanced Chronic Kidney Disease Patients with or without
Yoshio Kaku1, Susumu Ookawara1, Haruhisa Miyazawa1
1Division of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, Japan.
Insights
A new formula accurately estimates corrected calcium in advanced chronic kidney disease (CKD) patients, outperforming traditional methods. This improves serum calcium assessment for CKD G4-G5 and CKD G5D populations.
Area of Science:
- Nephrology
- Clinical Chemistry
Background:
- The conventional Payne formula for serum calcium correction is inadequate for advanced chronic kidney disease (CKD) patients.
- Accurate serum calcium estimation is crucial for managing CKD patients.
Purpose of the Study:
- To develop and validate a new formula for corrected serum calcium estimation in advanced CKD patients (G4-G5 and G5D).
- To improve the accuracy of calcium measurements in patients with impaired kidney function.
Main Methods:
- Collected 1,922 samples from CKD G4+G5 patients and 341 from CKD G5D patients.
- Measured total calcium (TCa), ionized calcium (iCa2+), and clinical parameters.
- Used stepwise multiple linear regression to derive a new formula, comparing it to measured corrected TCa.
Main Results:
- Devised new formulas for approximated corrected TCa for CKD G4+G5 and CKD G5D patients incorporating albumin, pH, phosphorus, and bicarbonate.
- Receiver operating characteristic analysis demonstrated high accuracy for the new formula in detecting specific corrected TCa ranges.
- Intraclass correlation coefficients showed superior agreement with the new formula compared to existing methods.
Conclusions:
- The newly developed approximated corrected TCa formula demonstrates superior agreement with measured corrected TCa in advanced CKD patients.
- This new formula offers a more reliable method for assessing calcium levels in CKD G4+G5 and CKD G5D populations.
Background:
The following calcium (Ca) correction formula (Payne) is conventionally used for serum Ca estimation: corrected total Ca (TCa) (mg/dl) = TCa (mg/dl) + [4 - albumin (g/dl)]; however, it is inapplicable to advanced chronic kidney disease (CKD) patients.
Methods:
1,922 samples in CKD G4 + G5 patients and 341 samples in CKD G5D patients were collected. Levels of TCa (mg/day), ionized Ca(2+) (iCa(2+)) (mmol/l) and other clinical parameters were measured. We assumed the corrected TCa to be equal to eight times the iCa(2+) value (measured corrected TCa). We subsequently performed stepwise multiple linear regression analysis using the clinical parameters.
Results:
The following formula was devised from multiple linear regression analysis. For CKD G4 + G5 patients: approximated corrected TCa (mg/dl) = TCa + 0.25 × (4 - albumin) + 4 × (7.4 - pH) + 0.1 × (6 - P) + 0.22. For CKD G5D patients: approximated corrected TCa (mg/dl) = TCa + 0.25 × (4 - albumin) + 0.1 × (6 - P) + 0.05 × (24 - HCO3 (-)) + 0.35. Receiver operating characteristic analysis showed the high values of the area under the curve of approximated corrected TCa for the detection of measured corrected TCa ≥8.4 mg/dl and ≤10.4 mg/dl for each CKD sample. Both intraclass correlation coefficients for each CKD sample demonstrated superior agreement using the new formula compared to the previously reported formulas.
Conclusion:
Compared to other formulas, the approximated corrected TCa values calculated from the new formula for patients with CKD G4 + G5 and CKD G5D demonstrates superior agreement with the measured corrected TCa.
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