Noninvasive assessment of bone health in Indian patients with chronic kidney disease

Comparison of Second- and Third-Generation Parathyroid Hormone Test Results in Patients with Chronic Kidney Disease

BACKGROUND In patients with chronic kidney disease (CKD), secondary hyperparathyroidism is assessed by measuring serum parathyroid hormone (PTH) levels. Well-established, recommended, second-generation intact parathyroid hormone (iPTH) tests are typical; rarely are more recent third-generation PTH 1-84 assays used. The agreement between results of the 2 tests in patients with CKD has not been sufficiently defined. MATERIAL AND METHODS This study aimed to compare Roche second- and third-generation PTH assays by establishing a quantitative relationship between the results of assays in patients with CKD and assessing degree of their correlation with kidney function and calcium-phosphate and bone metabolism parameters. In 205 patients with stages 3 to 5D CKD and 30 healthy controls, we measured levels of iPTH and PTH (1-84), creatinine, urea, cystatin C, calcium, inorganic phosphate, magnesium, alkaline phosphatase, bone alkaline phosphatase, osteocalcin, and ß-CrossLaps. RESULTS The third-generation PTH assay results were more than 40% lower than those obtained with the second-generation test in patients undergoing dialysis and approximately 30% lower in patients in the pre-dialysis period. PTH concentrations determined with both assays were almost to the same extent correlated with calcium-phosphate and bone metabolism parameters, and renal function indices. Formulas have been developed enabling 2-way conversion of PTH results determined with both the second- and third-generation PTH assays: For dialyzed patients, PTH (1-84)=0.5181iPTH+18.0595. Serum osteocalcin, ß-CrossLaps, and total calcium were independent predictors of PTH levels. CONCLUSIONS Correcting for the established quantitative differences, the second-and third-generation PTH tests can be used interchangeably, given the almost identical pathophysiological correlations of their results with calcium-phosphate and bone metabolism parameters.

Insights into the Association of Vitamin D Deficiency with Parathyroid Hormone Levels with Relevance to Renal Function and Insulin Resistance

Objective:

The rationale of the current study was to investigate whether this inverse association is agedependent and whether it has any role in modulating renal function and insulin resistance.

Methods:

To test this hypothesis, we have carried out a hospital based study enrolling 848 subjects (558 men and 290 women) with the mean age of 50.9 ± 15.9 y. Chemiluminometric competitive immune assays were performed using commercial kits to determine 25-OH vitamin D and Parathyroid Hormone (PTH) levels. Fasting glucose levels and serum creatinine were used to evaluate diabetes and renal function.

Results:

Vitamin D deficiency was predominant irrespective of age group (p = 0.21) and gender (p = 0.12). An inverse association between vitamin D and PTH was observed (r = -0.24) in middle age subjects (p = 0.02). The data segregation based on plasma vitamin D levels which were <20 ng/ml, 20.1- 30 ng/ml and >30 ng/ml confirmed the inverse association between vitamin D and PTH levels (ptrend: 0.007). Subjects with low plasma vitamin D and increased PTH exhibited elevated blood urea, serum creatinine and blood glucose. Subjects with 25-OHD deficiency showed a 3.03-folds (95% CI: 2.26- 4.07) and 2.09-fold (1.41-3.10) increased risk for diabetes and renal disease, respectively.

Conclusion:

Based on the results of the present study, it is suggested that those with vitamin D deficiency need to be evaluated for possible presence of renal dysfunction, diabetes/insulin resistance in addition to assessing their PTH status.

Profile of chronic kidney disease related-mineral bone disorders in newly diagnosed advanced predialysis diabetic kidney disease patients: A hospital based cross-sectional study

AIM

Chronic kidney disease related-mineral bone disorder (CKD-MBD) has been poorly studied in pre-dialysis Indian CKD population. There are limited data on the pattern of these disturbances in diabetic CKD patients. Therefore, a study was conducted to find out the profile of mineral bone disorders in T2DM patients with pre-dialysis CKD.

METHODS

In this cross-sectional design, diabetic patients with newly-diagnosed stage 4 and 5 CKD were evaluated. Serum levels of calcium, phosphorus, intact parathyroid hormone (iPTH), 25 hydroxy vitamin D and total alkaline phosphatase (ALP) were measured in all patients. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA).

RESULTS

A total of 72 eligible patients participated (44 males, 28 females; age 54.2±11.7). Patients with CKD Stage 5 had a lower level of corrected serum calcium and significantly higher level of inorganic phosphorus, total ALP and iPTH as compared to stage 4 patients. Overall, 38.5% were hypocalcemic, 31.43% were hyperphosphatemic. 24.2% of CKD subjects were vitamin D deficient (<10ng/ml) and 41.4% having vitamin D insufficiency (10-20ng/ml). In stage 4, hyperparathyroidism (iPTH>110pg/ml) was detected in nearly 43% of patients. In stage 5, only 32% patients was found to have hyperparathyroidism (iPTH>300pg/ml). There was a good correlation between iPTH and total ALP (r=0.5, p=0.0001) in this cohort. 25 (OH) vitamin D was inversely correlated with ALP (r=-0.39, P=0.001) and showed negative correlation with urine ACR (r=-0.37, P=0.002). As a group, the osteoporotic CKD subjects exhibited higher iPTH (220.1±153.8 vs. 119±108pg/ml, p<0.05) as compared to those who were osteopenic or had normal bone density. There was significant correlation between BMD and iPTH (adjusted r=-0.436; P=0.001). In the multivariate regression model, we found intact PTH to predict BMD even after adjustment of all the confounders.

CONCLUSION

The current study showed that adynamic bone disease is prevalent even in pre-dialysis CKD population. High bone turnover disease may not be the most prevalent type in diabetic CKD. However, it could contribute to the development of osteoporosis in CKD subjects. Serum total ALP can serve as a biochemical marker to identify pattern of bone turnover where intact PTH is not available.

Biochemical markers of mineral bone disorder in South African patients on maintenance haemodialysis

BACKGROUND AND OBJECTIVE

Despite the high mortality and morbidity associated with abnormalities in mineral and bone metabolism in haemodialysis patients, there is limited data on the pattern of mineral bone disorder in African CKD population. Therefore, the purpose of this study was to describe the pattern of mineral bone disease by evaluating biochemical parameters in patients on maintenance haemodialysis (MHD).

METHODS

We evaluated the serum/plasma intact parathyroid hormone (iPTH), corrected calcium, phosphate, total alkaline phosphatase (TALP) and 25 -OH vitamin D levels of two hundred and seven patients undergoing MHD at two dialysis centers in Johannesburg.

RESULTS

The MHD patients (133 men, 74 women) had a mean age of 54.5±15.6 years with a median dialysis vintage of 24 months (IQR, 12-48) and a mean kt/V of 1.45±0.28. The prevalence of hyperparathyroidism (iPTH >150 pg/ml), hyperphosphataemia, hypocalcaemia and 25-OH vitamin D deficiency (<30 ng/ml) was 73.4%, 57.0%, 20.3% and 80.7 % respectively. The combination of markers of bone turnover (iPTH >150pg/ml and TALP> 112 U/L) suggestive of high turnover bone disease, was present in 47.3 % of the study population. In multiple-logistic regression analysis, the odds ratio for developing hyperparathyroidism with hypocalcaemia and hyperphosphataemia were 5.32 (95% CI 1.10 - 25.9, P = 0.03) and 3.06(95 % CI 1.15 - 8.10, P=0.02) respectively. Ninety eight (47.3%) of the MHD patients had iPTH within the recommended kidney disease improving global outcome (KDIGO) guidelines.

CONCLUSION

Secondary hyperparathyroidism and 25-OH vitamin D deficiency were common in our haemodialysis patients. Hypocalcaemia and hyperphosphataemia were strong predictors for developing secondary hyperparathyroidism.

Assessment of bone turnover markers to predict mineral and bone disorder in men with pre-dialysis non-diabetic chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is commonly associated with disturbances in mineral metabolism and bone disease. Bone biopsy is the gold standard in diagnosing mineral bone disorder. Hence the search for non-invasive assessment of bone health gains importance. We undertook to assess the bone health in men with stage 4 and 5 chronic kidney Disease.

METHODS

We recruited 32 male subjects with Stage 4 and 5 chronic kidney disease and 32 age-matched healthy male controls. 25-hydroxyvitamin D, intact parathyroid hormone, and bone-specific alkaline phosphatase were assayed. Bone mineral density (BMD) was estimated using dual-energy X-ray absorptiometry.

RESULTS

CKD is associated with significantly higher levels of bone-specific alkaline phosphatase and intact parathyroid hormone and lower levels of 25-hydroxyvitamin D and bone mineral density, when compared to controls. In the multivariate linear regression model, bone-specific alkaline phosphatase emerged as an independent predictor of reduced BMD. Receiver Operator Characteristic analysis for prediction of reduced BMD in CKD showed both intact parathyroid hormone and bone-specific alkaline phosphatase have significant predicting power.

CONCLUSION

The combination of bone-specific alkaline phosphatase and intact parathyroid hormone has more significant predicting power and is a more reliable index for non-invasive assessment of bone health in men with chronic kidney disease, than either marker when used alone.