Bone alkaline phosphatase besides intact parathyroid hormone in hemodialysis patients--any advantage?

High serum β2‐microglobulin is a significant predictor of mortality in maintenance hemodialysis patients

BACKGROUND

Beta2-microglobulin, a novel marker of kidney function, predicts kidney failure and mortality in the general population. However, few studies have evaluated the association of serum β2-MG level with clinical outcome in maintenance hemodialysis (MHD) patients.

METHODS

This prospective cohort study enrolled 303 MHD patients to investigate the factors related to β2-MG and its relationship to mortality in MHD patients. Multivariate linear regression analysis was used to examine the factors related to β2-MG level. Multivariable Cox regression was used to calculate the hazard ratios for β2-MG on all-cause and cardiovascular mortality.

RESULTS

The median value of serum β2-MG was 44.6 mg/L (interquartile range 37.60-50.40 mg/L). During the follow-up period of 24 months, there were 48 all-cause deaths (23.0%), including 36 cardiovascular causes (75.0% of all deaths). Multiple linear regression showed that dialysis duration, serum creatinine, and alkaline phosphatase were independent predictors of serum β2-MG level. Kaplan-Meier analysis revealed that mortality in MHD patients was significantly higher in low albumin patients with β2-MG > 44.6 mg/L. Cox regression analysis showed that β2-MG was a significant predictor of all-cause mortality (HR = 1.122, 95% CI: 1.058-1.190, 𝑃 < 0.001) and cardiovascular mortality (HR = 1.145, 95%CI: 1.065-1.123, P < 0.001) in MHD patients with low albumin level after adjusting for confounding factors. However, our results showed that serum β2-MG was not associated with mortality in MHD patients with normal albumin level.

CONCLUSION

These results are supportive of the potential role of the serum β2-MG level as a predictor of mortality in MHD patients with low albumin.

Association Between Alkaline Phosphatase and Muscle Mass, Strength, or Physical Performance in Patients on Maintenance Hemodialysis

Introduction: Alkaline phosphatase (ALP) is an indicator for checking liver or bone disorders, but recent studies have shown the possibility of an additive indicator beyond the simple mineral-bone status in dialysis patients. The aim of the study was to evaluate the ALP level and various indicators for malnutrition, physical performance, or hospitalization in patients on hemodialysis (HD).

Methods: This study was an observational study (n = 84). We included all patients undergoing HD with the following criteria: age ≥ 20 years, duration of dialysis ≥ 6 months, ability to ambulate without an assistive device, ability to communicate with the interviewer, and no hospitalization within the last 3 months before enrollment. Furthermore, none of the patients had liver disease. We recommended abstinence of alcohol for ≥ 1 month for the duration of the study. The patients were divided into tertiles based on the ALP level. Muscle mass [appendicular muscle mass index using dual-energy X-ray absorptiometry (ASM/Ht²), thigh muscle area index using computed tomography (TMA/Ht²)], strength [handgrip strength (HGS)], and physical performance [gait speed (GS), sit-to-stand for 30-s test (STS30), 6-min walk test (6-MWT), or Short Physical Performance Battery test (SPPB)] were evaluated. The number of hospitalizations was also evaluated.

Results: The ALP level in the low, middle, and high tertiles was 50.5 ± 7.5, 69.8 ± 5.4, and 113.3 ± 47.3 IU/l, respectively. The high tertile group showed the poorest trends in ASM/Ht², TMA/Ht², HGS, GS, STS30, and 6-MWT compared to the other tertile groups. Logistic regression analysis showed that the high tertile group for low HGS, low GS, or low SPPB had a higher odds ratio compared to the other tertiles. Subgroup analyses according to age, sex and diabetes mellitus showed similar trends as in the total cohort. Hospitalization-free survival rates after 300 days in the high tertile and the other tertiles were 53.8 and 77.2%, respectively (P = 0.105).

Conclusion: The present study demonstrated that ALP is associated with muscle mass, strength, and physical performance in patients on maintenance HD. In addition, the trend showed better hospitalization-free survival in the low or middle tertiles than in the high tertile. ALP can be considered as a simple and useful indicator to detect malnutrition, physical performance, or hospitalization in patients on HD.

Influence of Hemodialysis Treatment on Biochemical Markers of Bone Disease

Introduction. Bone disease is a chronic complication of chronic kidney disease and major clinical problem in hemodialysis (HD) patients. The aim of our study was to assess the influence of treatment longevity on biochemical parameters of mineral and bone metabolism in HD patients, and to identify the most important parameters. Methods. The research was observational and retrospective, involved 70 patients, mean age 58.69±12.54, divided into groups in respect to the duration of dialysis treatment (Group I-5 years, Group II-5-10 years and Group III-over 10 years). Results. Serum phosphorus was increased, but the values tend to increase along with dialysis duration - (Group I: 1.93±0.45; Group II: 1.97±0.50; Group III: 2.01±0.37; p>0,05). Calcium values were also not significantly increased based on the duration of treatment [Group I: 2.3 (2.2-2.41); Group II: 2.46 (2.15-2.6), Group III: 2.35 (2.10-2.52)]. Dialysis and PTH correlated positively in the first group of patients (Rho=0.470, p=0.013). The values of calcium and alkaline phosphatase correlated positively in all patients (Rho=0.351, p=0.003). PTH was significantly higher in the second and third compared to the first group (p=0.009 and p=0.038, respectively), and there was no significant difference between the second and the third group. Interestingly, parathyroidectomized patients had higher PTH values compared to those without parathyroidectomy (557 vs. 359 pg/ml). Conclusion. The most reliable marker for clinical monitoring of bone disease in dialysis patients is PTH. The values of calcium and phosphorus are highly variable and not reliable parameters for bone disease follow-up.

A comparison of calcium acetate/magnesium carbonate and sevelamer-hydrochloride effects on fibroblast growth factor-23 and bone markers: post hoc evaluation from a controlled, randomized study

BACKGROUND

Different phosphate binders exert differing effects on bone mineral metabolism and levels of regulating hormones. The objective of this post hoc evaluation of the CALcium acetate MAGnesium carbonate (CALMAG) study was to compare the effects of calcium acetate/magnesium carbonate (CaMg) and a calcium-free phosphate binder, sevelamer-hydrochloride (HCl), on serum levels of fibroblast growth factor-23 (FGF-23) and markers of bone turnover.

METHODS

This secondary analysis of the controlled, randomized CALMAG study, comparing the effect of CaMg and sevelamer-HCl on serum phosphorus (P), aimed to investigate the parameters described above. The analysis included 204 patients who completed the initial study per protocol (CaMg, n = 105; sevelamer-HCl, n = 99).

RESULTS

The study showed that serum levels of FGF-23 were significantly reduced with CaMg and sevelamer-HCl, with no difference between groups at Week 25 [analysis of covariance (ANCOVA); log-intact FGF-23 (iFGF-23), P = 0.1573]. FGF-23 levels strongly correlated with serum P levels at all time points in both groups. The bone turnover parameters alkaline phosphatase (AP), bone AP (BAP), procollagen type 1 amino-terminal propeptide 1 (P1NP), osteoprotegerin (OPG), beta-crosslaps (β-CTX) and tartrate-resistant acid phosphatase 5b (TRAP 5b) increased significantly in the sevelamer-HCl group; they remained almost unchanged in the CaMg group, after the initial phase of P lowering (ANCOVA, P < 0.0001 for all except OPG, P = 0.1718).

CONCLUSIONS

CaMg and sevelamer-HCl comparably lower serum levels of iFGF-23. Changes in bone parameters were dependent on characteristics of the phosphate binder; in contrast with sevelamer-HCl, CaMg had no influence on bone turnover markers.

Kidney bone disease and mortality in CKD: revisiting the role of vitamin D, calcimimetics, alkaline phosphatase, and minerals

Recent evidence suggests that the traditional syndromes known as renal osteodystrophy, secondary hyperparathyroidism, and vitamin D deficiency are related to mortality in persons with moderate to advanced chronic kidney disease (CKD). The so-called 'kidney bone disease', also known as 'mineral and bone disorders', is defined to include bone disorders, mineral disarrays, and vascular calcification. We have identified 14 common and clinically relevant conditions of contemporary nature that are related to the kidney bone disease, including calcitriol (active vitamin D) deficiency, 25(OH)-vitamin D deficiency, biochemical hyperparathyroidism, relatively low parathyroid hormone (PTH) level, increased serum alkaline phosphatase (hyperphosphatasemia), elevated fibroblast growth factor (FGF)-23, high turnover bone disease, adynamic bone disease, uremic osteoporosis, vascular calcification, hyper- and hypophosphatemia, and hyper- and hypocalcemia. We present a critical review of these 14 conditions with emphasis on patient survival and other pertinent clinical outcomes. We also review unresolved controversies surrounding the management of these conditions by administration of nutritional vitamin D (ergocalciferol and cholecalciferol), vitamin D receptor activators (calcitriol, alphacalcidiol, doxercalciferol), D-mimetics (paricalcitol, maxacalcitol), calcimimetics (cinacalcet), recombinant PTH (teriparatide), and receptor activator of nuclear factor-kappaB ligand modulators (denosumab); compare mortality predictability of PTH and alkaline phosphatase; and examine potential risks of bone disorders and mineral disarrays in CKD patients.

Association of serum alkaline phosphatase and bone mineral density in maintenance hemodialysis patients

Recent studies indicate that serum alkaline phosphatase (AlkPhos), a surrogate of high turnover bone disease, is associated with coronary artery calcification and death risk in maintenance hemodialysis (MHD) patients. The association between AlkPhos and bone mineral density (BMD) is not well studied. We studied the association between AlkPhos and dual-energy X-ray absorptiometry-assessed BMD in a group of MHD patients in Southern California. In 154 MHD patients, aged 55.3 +/- 13.6 years, including 42% women, 38% Hispanics, 42% African Americans, and 55% diabetics, the mean serum AlkPhos was 121 +/- 63 U/L (median: 101, Q(25-75): 81-141); 36% had AlkPhos>/=120 U/L and 50% had a total T-score< or =-1. Whereas the total BMD did not correlate with age (r=0.01, P=0.99) or body mass index (r=0.10, P=0.22), it correlated negatively with AlkPhos (r=-0.25, P=0.002), including after multivariate adjustment (r=-0.24, P=0.003). The proportion of patients with a high coronary artery calcification score>400 was incrementally higher across worsening BMD tertiles (P trend=0.04). The BMD was significantly worse in MHD patients with serum AlkPhos> or =120 U/L compared with <120 U/L (1.01 +/- 0.016 vs. 1.08 +/- 0.013 g/cm(2), respectively, P<0.001). The multivariate adjusted odds ratio of AlkPhos> or =120 U/L for having a total T-score<-1.0 was 2.3 (1.1-4.8, P=0.037). Among routine clinical and biochemical markers, serum AlkPhos> or =120 U/L was a better predictor of total T-score< or =-1 in MHD patients. An association exists between higher serum AlkPhos and worse dual-energy X-ray absorptiometry-assessed BMD in MHD patients. Given these findings, studies are indicated to examine whether interventions that lower serum AlkPhos improve BMD in MHD patients.

Serum alkaline phosphatase predicts mortality among maintenance hemodialysis patients

Several observational studies have demonstrated that serum levels of minerals and parathyroid hormone (PTH) have U- or J-shaped associations with mortality in maintenance hemodialysis patients, but the relationship between serum alkaline phosphatase (AlkPhos) and risk for all-cause or cardiovascular death is unknown. In this study, a 3-yr cohort of 73,960 hemodialysis patients in DaVita outpatient dialysis were studied, and the hazard ratios for all-cause and cardiovascular death were higher across 20-U/L increments of AlkPhos, including within the various strata of intact PTH and serum aspartate aminotransferase. In the fully adjusted model, which accounted for demographics, comorbidity, surrogates of malnutrition and inflammation, minerals, PTH, and aspartate aminotransferase, AlkPhos > or =120 U/L was associated with a hazard ratio for death of 1.25 (95% confidence interval 1.21 to 1.29; P < 0.001). This association remained among diverse subgroups of hemodialysis patients, including those positive for hepatitis C antibody. A rise in AlkPhos by 10 U/L during the first 6 mo was incrementally associated with increased risk for death during the subsequent 2.5 yr. In summary, high levels of serum AlkPhos, especially >120 U/L, are associated with mortality among hemodialysis patients. Prospective controlled trials will be necessary to test whether serum AlkPhos measurements could be used to improve the management of renal osteodystrophy.

Comparison of Biochemical Markers of Bone Turnover in Patients on Continuous Ambulatory Peritoneal Dialysis and Maintenance Hemodialysis

The aim of this study was to compare the biochemical markers of bone formation - bone isoenzyme alkaline phosphatase, /BALP/ bone resorption - tartarat resistant acid phosphatase /TRAP/ and parameters of bone turnover (Ca, P and iPTH) between 108 patients on continuous ambulatory peritoneal dialysis (CAPD) and 112 patients on hemodialysis (HD). Parameters were determined by spectrophotometry (TRAP, Ca, P), electrochemiluminiscent method (iPTH) and electrophoresis (BALP). There was significant correlation between BALP levels of CAPD patients and Ca values of HD patients (r = 0.216, p < 0.05), but comparison of P, iPTH and BALP showed no significant difference between the groups. We found significant correlation between BALP and TRAP (r = 0.570, p < 0.01) and BALP and iPTH values (r = 0.551, p < 0.01) in HD patients. Also, significant correlations in CAPD patients between BALP and TRAP (r = 0.194, p < 0.05) and BALP and iPTH values (r = 0.283, p < 0.01) were found. Our results suggest that the effect of CAPD and HD on bone turnover may be monitored most conclusively via BALP levels. This biochemical marker is a very good index of bone turnover in patients undergoing dialysis and it could indicate an early stage of decreased bone turnover.