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Factors affecting the relationship between ionized and corrected calcium levels in peritoneal dialysis patients: a
Masamitsu Morishita1, Yukio Maruyama2, Masatsugu Nakao2
1Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, Tokyo, 105-8461, Japan. m.morishita0319@gmail.com.
Insights
In peritoneal dialysis (PD) patients, lower ionized calcium/corrected calcium (iCa/cCa) ratios correlate with reduced residual renal function (RRF). This highlights the need for careful CKD-MBD management in PD patients with declining RRF.
Area of Science:
- Nephrology
- Endocrinology
- Biochemistry
Background:
- Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a significant concern in end-stage renal disease patients, increasing cardiovascular risk.
- Current clinical practice often monitors total or corrected calcium (cCa) rather than biologically active ionized calcium (iCa) for CKD-MBD management.
- Previous research indicated differing iCa/cCa ratios between hemodialysis and peritoneal dialysis (PD) patients.
Purpose of the Study:
- To investigate factors influencing the iCa/cCa ratio in PD patients.
- To inform potential modifications in CKD-MBD management strategies for PD patients.
- To address the lack of prior research on iCa/cCa ratio determinants in PD.
Main Methods:
- A retrospective cross-sectional study design was employed.
- Background and laboratory data, including iCa, were collected from routine outpatient visits.
- Multiple regression analysis and multiple imputation were used to identify influencing factors and handle missing data.
Main Results:
- Lower iCa/cCa ratios were associated with longer PD duration and higher pH.
- Urine volume and weekly renal Kt/V were lower in patients with lower iCa/cCa ratios.
- Weekly renal Kt/V and pH were identified as independent factors affecting the iCa/cCa ratio (p < 0.01).
Conclusions:
- PD patients with lower residual renal function (RRF) exhibited lower iCa levels despite similar cCa levels.
- These findings underscore the importance of cautious assessment and management of CKD-MBD in PD patients, particularly those with diminished RRF.
- The study highlights the complex interplay of factors affecting calcium levels in PD patients.
Background:
Chronic kidney disease-mineral and bone disorder (CKD-MBD) management in patients with end-stage renal disease is important owing to the risk of cardiovascular diseases. In clinical practice, we manage patients not by monitoring the levels of biologically active ionized calcium (iCa) but by monitoring total serum calcium or corrected calcium (cCa). We previously reported that iCa/cCa ratio was different between patients with hemodialysis and those with peritoneal dialysis (PD). In PD patients, several factors are expected to affect iCa/cCa ratio. Therefore, modifying the strategy to achieve better CKD-MBD management might be necessary; however, no reports have studied this to date. Therefore, we investigated the factors influencing iCa/cCa ratio in PD patients.
Methods:
This retrospective cross-sectional study examined background and laboratory data, including iCa, collected at routine outpatient visits. The patients were divided into the first, second, and third tertile of iCa/cCa ratio groups to compare patient background and laboratory data. Multiple regression analysis was used to investigate the factors influencing iCa/cCa ratio. We used multiple imputation to deal with missing covariate data.
Results:
In total, 169 PD patients were enrolled. In PD patients with lower iCa/cCa ratio, PD duration was longer and pH was higher. Urine volume and weekly renal Kt/V were lower in the patients with lower iCa/cCa ratio than in those with higher iCa/cCa ratio. iCa/cCa ratio and weekly renal Kt/V were directly correlated (r = 0.41, p < 0.01), and weekly renal Kt/V and pH were independent factors affecting iCa/cCa ratio (t = 2.86, p < 0.01 and t = - 5.42, p < 0.01, respectively).
Conclusions:
iCa levels were lower in PD patients with lower residual renal function (RRF) even though their cCa levels were equal to those with maintained RRF, warranting caution in the assessment and management of CKD-MBD in PD patients.
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