Calcium, phosphate and parathyroid metabolism in kidney transplanted patients.
BACKGROUND
Impaired kidney function is common in kidney-transplanted patients and complications of chronic kidney disease (CKD), such as mineral and bone disorders (MBD) are also prevalent in this population. Similarly to other stages of CKD, increasing evidence supports the association between MBD and cardiovascular risk after kidney transplantation as well. Still, little is known about the prevalence, clinical correlates of MBD and its management in transplanted patients. In this study, we aimed to examine the characteristics of MBD and its associations with clinical parameters in a large prevalent cohort of patients after kidney transplantation.


METHODS
Nine hundred and ninety stable patients followed at a single kidney transplant outpatient clinic were included in the study. Detailed medical history, demographic data and routine laboratory results, including Ca, P and intact PTH were collected. Estimated GFR was calculated using the abbreviated MDRD formula, patients were stratified into three groups based on eGFR. Target levels for Ca, P and iPTH were based on CKD stages according to the NKF-K/DOQI guidelines. Standard statistical procedures, binomial and multinomial regressions were used in the analysis.


RESULTS
The mean age was 51 years, 57% were males and 21% were diabetic, with 72 months (median) post-transplantation. Most of the patients were in CKD stage 3. Serum phosphorus showed strong negative correlation with graft function in CKD stages 4-5 (r = -0.633, P < 0.001). Hyperphosphatemia was independently associated with the time spent on dialysis before transplantation, serum iPTH and CKD stages 4-5. iPTH showed negative correlation with eGFR in CKD stages 3-5 (rho = -0.289, P < 0.001) and weak positive correlation with time spent on dialysis prior to transplant (rho = 0.114, P < 0.001). Both hyperparathyroidism (42%) and relative hypoparathyroidism (15%) were frequent. The prescription of P-binders (6%) and vitamin D analogs (33%) was sporadic.


CONCLUSIONS
Disturbances of bone and mineral metabolism after transplantation are prevalent and are strongly correlated with the kidney function, similarly to non-transplanted CKD patients. MBD in this population is not adequately managed.
Ambrus
Csaba
C
Department of Nephrology, University Health Network, University of Toronto, Toronto, Canada.
Molnar
Miklos Zsolt
MZ
Czira
Maria Eszter
ME
Rosivall
Laszlo
L
Kiss
Istvan
I
Remport
Adam
A
Szathmari
Miklos
M
Mucsi
Istvan
I
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism; D001774:Blood Chemical Analysis; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D016009:Chi-Square Distribution; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006084:Graft Rejection; D006085:Graft Survival; D006801:Humans; D007677:Kidney Function Tests; D016030:Kidney Transplantation / Q000009:adverse effects* / Q000379:methods; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010281:Parathyroid Hormone / Q000032:analysis / Q000378:metabolism*; D010710:Phosphates / Q000032:analysis / Q000378:metabolism*; D011183:Postoperative Complications / Q000175:diagnosis / Q000453:epidemiology; D011237:Predictive Value of Tests; D011336:Probability; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D018570:Risk Assessment; D015996:Survival Rate; D013997:Time Factors
D015415:Biomarkers; D010281:Parathyroid Hormone; D010710:Phosphates; D002118:Calcium
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