KDIGO Clinical Practice Guideline for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD)

Chapter 5: Evaluation and treatment of kidney transplant bone disease

Kidney International (2009) 76, S100-S110; doi:10.1038/ki.2009.193

INTRODUCTION

As the number and survival of kidney transplant recipients increase, new challenges arise for overall management. Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a common morbidity in patients with a kidney transplant, and pre-existing CKD-MBD may adversely affect bone health, even with normal kidney allograft function. In addition, most kidney transplant recipients have some degree of CKD, and thus CKD-MBD may be present. However, transplant-specific therapies, especially corticosteroids, may further affect CKD-MBD management.

RECOMMENDATIONS

5.1 In patients in the immediate post-kidney-transplant period, we recommend measuring serum calcium and phosphorus at least weekly, until stable (1B).

5.2 In patients after the immediate post-kidney-transplant period, it is reasonable to base the frequency of monitoring serum calcium, phosphorus, and PTH on the presence and magnitude of abnormalities, and the rate of progression of CKD (not graded).Reasonable monitoring intervals would be:

• In CKD stages 1-3T, for serum calcium and phosphorus, every 6-12 months; and for PTH, once, with subsequent intervals depending on baseline level and CKD progression.
• In CKD stage 4T, for serum calcium and phosphorus, every 3-6 months; and for PTH, every 6-12 months.
• In CKD stage 5T, for serum calcium and phosphorus, every 1-3 months; and for PTH, every 3-6 months.
• In CKD stages 3-5T, measurement of alkaline phosphatases annually, or more frequently in the presence of elevated PTH (see Chapter 3.2).

In CKD patients receiving treatments for CKD-MBD, or in whom biochemical abnormalities are identified, it is reasonable to increase the frequency of measurements to monitor for efficacy and side-effects (not graded).

It is reasonable to manage these abnormalities as for patients with CKD stages 3-5 (not graded) (see Chapters 4.1 and 4.2).

5.3 In patients with CKD stages 1-5T, we suggest that 25(OH)D (calcidiol) levels might be measured, and repeated testing determined by baseline values and interventions (2C).

5.4 In patients with CKD stages 1-5T, we suggest that vitamin D deficiency and insufficiency be corrected using treatment strategies recommended for the general population (2C).

5.5 In patients with an estimated glomerular filtration rate greater than approximately 30 ml/min per 1.73 m², we suggest measuring BMD in the first 3 months after kidney transplant if they receive corticosteroids or have risk factors for osteoporosis as in the general population (2D).

5.6 In patients in the first 12 months after kidney transplant with an estimated glomerular filtration rate greater than approximately 30 ml/min per 1.73 m² and low BMD, we suggest that treatment with vitamin D, calcitriol/alfacalcidol, or bisphosphonates be considered (2D).

• We suggest that treatment choices be influenced by the presence of CKD-MBD, as indicated by abnormal levels of calcium, phosphorus, PTH, alkaline phosphatases, and 25(OH)D (2C).
• It is reasonable to consider a bone biopsy to guide treatment, specifically before the use of bisphosphonates due to the high incidence of adynamic bone disease (not graded).

There are insufficient data to guide treatment after the first 12 months.

5.7 In patients with CKD stages 4-5T, we suggest that BMD testing not be performed routinely, because BMD does not predict fracture risk as it does in the general population and BMD does not predict the type of kidney transplant bone disease (2B).

5.8 In patients with CKD stages 4-5T with a known low BMD, we suggest management as for patients with CKD stages 4-5 not on dialysis, as detailed in Chapters 4.1 and 4.2 (2C).

Summary of rationale for recommendations

• The risk of fractures after kidney transplant is high.
• The etiology of transplant bone disease is multifactorial and most patients have pre-existing CKD-MBD.
• In non-kidney-transplant recipients, a low BMD or loss of BMD predicts fracture, but data are lacking for kidney transplant recipients.
• There are no randomized controlled trial (RCT) data examining bone-specific therapies on patient-level outcomes, including mortality or fractures, in patients receiving kidney transplantation.
• Treatment with calcium, calcitriol, or vitamin D analogs, and/or bisphosphonates, has been suggested to improve BMD in kidney transplant recipients. However, bone biopsy studies are limited. cir;
  • A small study of calcitriol showed worsened bone turnover, but improved mineralization. cir;
  • A small study of treatment with bisphosphonates showed worsened bone turnover and mineralization.
• It is unclear how to identify those kidney transplant patients who would benefit more or less from specific treatments, making it difficult to assess the risk-benefit ratio of those treatments.
• The absence of RCTs that show fracture prevention and heterogeneity within post-kidney-transplantation bone disease prevents the generalization of therapeutic strategies across patients and extrapolation from non-kidney-transplant studies. Therefore, this remains a weak recommendation.

BACKGROUND

Biochemical abnormalities

Biochemical abnormalities are common after transplant, but less documented than in patients on dialysis. It is probably useful to distinguish the time period immediately after kidney transplant, with rapidly changing GFR and concomitantly given therapies, from the subsequent time period when a more stable graft function has been achieved. The magnitude of CKD-MBD before transplant, the degree of kidney function recovery, and the effects of immunosuppressive and other therapies create a heterogeneous patient population. The scope and magnitude of the biochemical abnormalities of CKD-MBD fluctuate dramatically in the early post-transplant period compared with the late post-transplant period, the latter depending on the level of kidney function. Hypophosphatemia occurs in a large proportion of patients immediately after transplantation, but once kidney function has become stabilized, serum phosphorus returns to the normal range in most of them. Serum calcium tends to increase after transplant and then stabilizes at the higher end of the normal range within 2 months. PTH levels decrease significantly during the first 3 months after transplant but typically stabilize at elevated values after 1 year. Low levels of 1,25(OH)2D typically do not reach normal values until almost 18 months after transplant.⁴⁴⁶ There are no large databases in which these data are routinely collected and therefore can be systematically evaluated. Thus, most reports are single-center studies.

Bone

Abnormalities of bone are nearly uniformly observed, but the etiology and pathology are widely variable. Post-transplant bone disease represents an important complication observed in a substantial proportion of patients. Early studies have shown a rapid decrease in BMD in the first 6-12 months after successful kidney transplantation, and continued loss--albeit at a lower rate--for many years.⁴⁴⁷ As a consequence, fractures are common and associated with substantial morbidity.

The etiology of transplant bone disease is multifactorial. Patients come to transplantation with pre-existing bone disease of CKD (CKD-MBD), which is not always improved by transplantation. In addition, new insults to bone occur, including the potentially deleterious effects of various immunosuppressive agents, the impaired kidney function (CKD) frequently observed in kidney transplant patients, and other factors particular to each patient, such as post-menopausal status, presence of diabetes, smoking, physical activity, and duration of dialysis and transplantation.⁴⁴⁸ Previous studies in kidney transplant patients have shown a correlation between the cumulative dose of glucocorticoids and BMD. On the basis of a few bone biopsy studies in transplant patients, glucocorticoids seem to be the primary determinant of subsequent bone volume and turnover. Thus, the cumulative and mean prednisone dose correlated negatively with bone turnover, whereas there was no correlation with cyclosporine cumulative dose or serum PTH.⁴⁴⁹ The possible role of calcineurin inhibitors, such as cyclosporine or tacrolimus, remains incompletely studied, with contradictory reports on their effects on bone turnover.⁴⁴⁹

Vascular calcification

Arterial calcification is also common after a kidney transplant, but is often due to the effects of the uremic state and dialysis rather than the transplant itself and, overall, is poorly studied in this population. In renal transplant recipients (CKD stages 1-5T), only one prevalence study was identified, showing a prevalence of calcification of 24.4%.450 Although this cross-sectional study was large (n = 1117), calcification was assessed by a posterio-anterior plain abdominal X-ray examination of the aorto-iliac region, which is likely to be less sensitive than computed tomography-based imaging methods and gives only semiquantitative information. In addition, one of the major difficulties in interpreting calcification in the transplant population is the carryover effect from CKD stage 5 or stage 5D. Currently, only one preliminary study is available, suggesting that the progression of cardiovascular calcification may be halted after renal transplantation.⁴⁵¹ Thus, much remains to be learned.

The following tables are found at the end of this chapter: Table 39 summarizes the RCTs of treatments in children with CKD (stages 1-5T). The evidence matrix, a table that describes the methodologic quality of the included studies, and the evidence profile, a table that provides an overall assessment of the quality of the evidence and balance of potential benefits and harm are Tables 40, 41 for calcitriol or vitamin D analogs; and Tables 42, 43 for bisphosphonates. Studies of treatments for CKD-MBD in transplant recipients reviewed for this topic are further described in detail in the Supplementary Tables 46-53.

 

 

 

 

RATIONALE

5.1 In patients in the immediate post-kidney-transplant period, we recommend measuring serum calcium and phosphorus at least weekly, until stable (1B).

Similar to what has been described for CKD stage 3-5 patients with CKD-MBD, in kidney transplant recipients, serum levels of calcium, phosphorus, total CO2, and PTH should be closely monitored in all patients regardless of graft function. During the first week after kidney transplantation, serum levels of calcium and phosphorus should be measured at least weekly. Many, if not most, kidney transplant recipients develop persistently low levels of serum phosphorus (<3.1 mg/dl or 1.0 mmol/l) in the post-transplant period. They should be considered for treatment with phosphate supplementation. However, phosphate administration is not without risk, and caution should be exerted, as it may exacerbate an already existing secondary hyperparathyroidism (HPT). Therefore, every attempt should be made to prescribe the minimum doses. Patients with severe secondary HPT before the transplant will continue to have excessive PTH secretion from large hyperplastic glands. With a new kidney, there will now be enhanced renal reabsorption of calcium and hypercalcemia may ensue. Also, there will be reduced tubular phosphate reabsorption. Thus, during the immediate post-transplant period, wide fluctuations of serum calcium and phosphorus may be seen and thus frequent monitoring is needed.

5.2 In patients after the immediate post-kidney-transplant period, it is reasonable to base the frequency of monitoring serum calcium, phosphorus, and PTH on the presence and magnitude of abnormalities, and the rate of progression of CKD (not graded).

Reasonable monitoring intervals would be:

• In CKD stages 1-3T, for serum calcium and phosphorus, every 6-12 months; and for PTH, once, with subsequent intervals depending on baseline level and CKD progression.
• In CKD stage 4T, for serum calcium and phosphorus, every 3-6 months; and for PTH, every 6-12 months.
• In CKD stage 5T, for serum calcium and phosphorus, every 1-3 months; and for PTH, every 3-6 months.
• In CKD stages 3-5T, measurement of alkaline phosphatases annually, or more frequently in the presence of elevated PTH (see Chapter 3.2).

In CKD patients receiving treatments for CKD-MBD, or in whom biochemical abnormalities are identified, it is reasonable to increase the frequency of measurements to monitor for efficacy and side-effects (not graded).

It is reasonable to manage these abnormalities as for patients with CKD stages 3-5 (not graded) (see Chapters 4.1 and 4.2).

Patients with a kidney transplant usually have some degree of CKD and, therefore, CKD-MBD may be present. However, there are no clinical trials that have specifically addressed the optimal frequency of monitoring in the CKD or CKD transplant population. Thus, on the basis of the prevalence of abnormalities and the risks associated with those abnormalities, the management of the biochemical abnormalities of CKD-MBD after transplant should be similar to that proposed for nontransplant CKD.

A recent study of 303 kidney transplant recipients in the United States found that 11-25% of patients had abnormal serum calcium or CaXP in the first year after transplant, and 24% of recipients with an eGFR between 40 and 60 ml/min per 1.73 m² had intact PTH levels >130 pg/ml (13.8 pmol/l) at 1 year after kidney transplant.⁴⁵² Another series from the United Kingdom⁴⁵³ evaluated 244 kidney transplant recipients: 104 in the first year, and the remainder more than 1 year after transplant. Hypercalcemia was present in 40% of recently transplanted recipients and 25% of long-term patients. Hypophosphatemia was very common in the immediate post-transplant period, but normalized within the first year in most series, although a urinary phosphate leak often remained despite normal serum levels.⁴⁵⁴ A larger cohort from Switzerland455 evaluated 823 kidney transplant recipients, on average 7 years after transplant. They found that only 27% of the population had a PTH within normal range (that is, 15-65 pg/ml (1.6-6.9 pmol/l)), whereas 70% had HPT (PTH>65 pg/ml (>6.9 pmol/l)) and 2.8% were hypoparathyroid (PTH<15 pg/ml (<1.6 pmol/l)). Serum phosphorus was within normal range in 74% of the patients (0.85-1.45 mmol/l), and increased in only 3.6% of the patients. Finally, serum calcium was within normal range in most patients (85.9%), with only 2.8 and 11.3% of the patients being hypocalcemic and hypercalcemic, respectively. Thus, disorders of mineral metabolism may persist many years after transplantation.

There is a paucity of data describing the risk relationship of biochemical abnormalities of CKD-MBD and mortality in patients after kidney transplantation. A study in Austria of 773 patients with kidney transplant found no relationship between serum calcium, phosphorus, or PTH and mortality.⁴⁵⁶ However, they did find that patients with the highest quintile of phosphorus had increased risk of kidney allograft loss. Similarly, those with the highest quintile of calcium also had increased risk of kidney allograft loss, which is similar to other reports in which hypercalcemia was associated with both graft loss and recipient death.⁴⁵² Clearly, more data are needed to fully understand the possible significance of these relationships.

From a management perspective, there are no RCTs that specifically enrolled transplant recipients who met our inclusion criteria. Thus, approaches similar to those in nontransplant CKD should be taken, with some special considerations. Hypercalcemia after kidney transplantation is usually due to HPT that persists from the preceding CKD period. Increased serum calcium concentration can persist for years after transplantation. In patients with nonsuppressible nodular parathyroid hyperplasia, persistently elevated PTH levels after restoration of normal renal function with a transplant may have a primary role in maintaining a high bone turnover. Parathyroid gland hyperplasia, especially autonomous parathyroid growth, does not easily resolve after establishment of sufficient renal function, except in mild cases or when secondary to vitamin D deficiency. In 30-50% of transplant recipients, abnormal PTH secretion persists. When it causes hypercalcemia, it may require parathyroidectomy.^{457, 458, 459 and 460} In general, the same principles we have discussed for the management of patients with CKD stages 3-5 with CKD-MBD will apply for patients with CKD stages 3-5T.

5.3 In patients with CKD stages 1-5T, we suggest that 25(OH)D (calcidiol) levels might be measured, and repeated testing determined by baseline values and interventions (2C).

25(OH)D levels were measured in 244 renal transplant recipients and divided into two groups: 104 recently transplanted (less than 1 year) and 140 long term.⁴⁵³ Vitamin D insufficiency (15-30 ng/ml or 40-75 nmol/l) was present in 29 and 43% of recent and long-term kidney transplant recipients, deficiency (4.8-15.6 ng/ml or 12-39 nmol/l) in 56 and 46%, and severe deficiency (<4.8 ng/ml or 12 nmol/l) in 12 and 5%, respectively. Thus, vitamin D deficiency is common after transplant, and an initial assessment of status is reasonable.

5.4 In patients with CKD stages 1-5T, we suggest that vitamin D deficiency and insufficiency be corrected using treatment strategies recommended for the general population (2C).

Vitamin D deficiency and insufficiency are associated with cardiovascular disease, autoimmune disorders, malignancies, bone disease and musculoskeletal weakness, and insulin resistance.⁴⁶¹ Unfortunately, there are no RCTs of vitamin D supplementation in patients with a kidney transplant evaluating end points other than bone health (see recommendation 5.6 for bone health). However, given the magnitude of vitamin D deficiency and the high prevalence of many of the disorders associated with vitamin D deficiency in the general population, the Work Group felt that it was reasonable to treat deficiency, if found. Thus, supplementation with either ergocalciferol or cholecalciferol is recommended, but the optimal treatment regimen is not known,⁴⁶² and neither is the sufficient level of calcidiol well defined (see Chapter 3.1). It is also important to point out that the primary source of vitamin D is sunlight, and that the increased risk of skin cancer in kidney transplant patients mandates the use of appropriate sun-screen protection, further increasing the need for oral intake of vitamin D.⁴⁶³

5.5 In patients with an estimated glomerular filtration rate greater than approximately 30 ml/min per 1.73 m², we suggest measuring BMD in the first 3 months after kidney transplant if they receive corticosteroids, or have risk factors for osteoporosis as in the general population (2D).

Post-transplant bone disease is a complex disorder that extends beyond simple alterations in BMD. It includes systemic and local derangements of bone and mineral metabolism that can be detected and treated appropriately. The management of bone disease after kidney transplantation should take into account its pathophysiology, with particular focus on three different phases: (i) optimal treatment of CKD-MBD before kidney transplantation; (ii) prevention of bone loss during the first year after transplantation; and (iii) treatment of decreased bone mass thereafter.

There are no studies that directly address fracture prevention, hospitalizations, or mortality related to CKD-MBD in kidney transplant recipients. There is only one study that shows low BMD, as assessed by dual energy X-ray absorptiometry (DXA), to be predictive of fracture risk in kidney transplant recipients. This recent study evaluated 238 renal transplant patients with CKD stages 1-5T who underwent 670 DXA investigations of the hip. Fractures were assessed by a questionnaire. Osteopenia and an absolute bone density below 0.9 g/cm² in the hip region conferred an increased risk of fracture.⁴⁶⁴ However, the Work Group felt that this study was inadequate to determine whether DXA had a high enough predictive value of fracture to be routinely used, because of the bias of repeated DXA evaluations counted as independent measures and the nonsystematic assessment of fractures. It is worth noting that reductions in BMD have been associated with an increased fracture rate in studies of osteoporosis in women in association with post-menopausal status, in men treated with glucocorticoids, and in heart- or liver-transplant recipients. However, the etiology of post-transplant kidney bone disease is likely influenced by CKD-MBD from the pretransplant dialysis period, and ongoing CKD-MBD after transplant, given that most patients have some impairment of kidney function. Thus, the studies from the general population and other solid organ transplantation may not be generalizable to the kidney transplant population. In addition, there are no treatments in these patients that show fracture reduction (see Recommendation 5.6). Thus, the Work Group felt that DXA should be reserved for high-risk populations, including those receiving significant doses of corticosteroids, or those with risk factors for osteoporosis in the general population (see Chapter 3.2). In addition, the Work Group felt that DXA screening after transplant should only be done in individuals with a well-functioning allograft (CKD stages 1-3T), as patients with CKD stages 4-5T will be more likely to have abnormal bone quality from CKD-MBD, with unknown impact on the predictive value of DXA.

5.6 In patients in the first 12 months after kidney transplant with an estimated glomerular filtration rate greater than approximately 30 ml/min per 1.73 m² and low BMD, we suggest that treatment with vitamin D, calcitriol/alfacalcidol, or bisphosphonates be considered (2D).

• We suggest that treatment choices be influenced by the presence of CKD-MBD, as indicated by abnormal levels of calcium, phosphorus, PTH, alkaline phosphatases, and 25(OH)D (2C).
• It is reasonable to consider a bone biopsy to guide treatment, specifically before the use of bisphosphonates due to the high incidence of adynamic bone disease (not graded).

There are insufficient data to guide treatment after the first 12 months.

As detailed below, unfortunately, there are no RCTs that show the beneficial or harmful effects of bone-protective agents on patient-level outcomes, in particular fractures, hospitalizations, or mortality. Studies that examined the effects of calcitriol or vitamin D analogs to prevent transplant bone disease found an improvement in BMD and no adverse events (AEs) of bone.^{465, 466, 467 and 468} Studies that examined the effects of bisphosphonates to prevent transplant bone disease found an improvement in BMD,^{165, 469} but possible AEs of bone histology, increasing the risk of adynamic bone disease.⁴⁶⁹ There are only inconsistent or low-quality data showing positive effects of vitamin D, calcitriol, vitamin D analogs, or bisphosphonates on BMD in established transplant bone disease.^{470, 471} Given that BMD is not a well-validated surrogate marker of fracture risk in the transplant patient (and is not even an accepted end point for drug treatments in the general population), and that no studies evaluate fracture as an end point in transplant recipients, this recommendation can only be weak. In addition, clinicians should be aware of the complexity and heterogeneity of transplant bone disease and consider the use of bone biopsy and other biochemical abnormalities of CKD-MBD to guide therapeutic choices rather than only focusing on DXA.

Preventive therapy

Use of vitamin D, calcitriol, and its analogs. Each of the trials in which vitamin D, calcitriol, or its analogs were administered as preventive therapy assessed changes in BMD as the primary outcome.

There were no studies evaluating vitamin D therapy specifically in kidney transplant recipients that met our inclusion criteria, but a meta-analysis published in 1999, in patients treated with steroids for multiple reasons, supported efficacy in improving BMD of the lumbar spine.⁴⁶⁵ This meta-analysis compared all RCTs lasting at least 6 months (and reporting extractable results) of patients receiving oral corticosteroids and treated with vitamin D. The study found a moderate beneficial effect of vitamin D plus calcium vs no therapy or vs calcium alone (nine trials: effect size 0.60; 95% CI 0.34, 0.85; P<0.0001). In a comparison of vitamin D with other osteoporosis therapies, bisphosphonates were more effective than vitamin D (six trials: effect size 0.57; 95% CI 0.09, 1.05). Thus, the Work Group felt that vitamin D supplementation is a reasonable and safe treatment choice for patients with low BMD.

In three studies in renal transplant recipients,^{466, 467 and 468} a positive change in BMD was observed in the calcitriol and alfacalcidol groups vs the 'no treatment' or placebo groups. No fracture data were recorded in any of these studies. The RCTs are detailed in Tables 40, 41 and Supplementary Tables 46-49. No clinically important clinical outcomes such as mortality, hospitalizations, or fractures were evaluated. Only BMD as a surrogate marker for fractures was determined. In addition, most of the studies either lacked or did not define randomization, or there were inconsistencies between the text and the tables. Some studies did not provide any baseline data or the data were incomplete. Thus, the overall quality of the evidence was classified as low. As reported, no significant AEs were observed, except for mild hypercalcemia in the study by Josephson et al.⁴⁶⁸ No patients were withdrawn from the study because of secondary effects. No deleterious effect on kidney graft function was observed.

Bisphosphonates. Two studies in 152 patients evaluated the role of bisphosphonates as preventive therapy after kidney transplantation (Tables 42, 43).⁴⁷⁰ This study enrolled 45 patients, with only 30 of them completing the trial. This RCT met our inclusion criteria because bone biopsies were an evaluated end point. The mean time after transplantation was 118.7 months in the treatment group and 133 months in the control group. Although significant improvement in BMD was observed after 1 year in the treatment group, no differences were observed between the treatment and nontreatment groups. No fracture data were reported. Thus, the overall quality of the evidence is low. After 1 year of treatment, patients in the treatment group had a suppression of serum PTH, together with an increase in serum calcium (but within normal limits), as compared with the no-treatment group. The bone biopsy results showed that bone turnover was better in 43% of the control biopsies and 12% of the calcitriol biopsies, but worse in 28% of the control biopsies and 50% of the calcitriol biopsies. The study also described a decrease in osteoclast surfaces that represents a secondary index of turnover. Therefore, if a decrease in the osteoclast surface is accompanied by a drop in the bone formation rate into the adynamic range, then the overall turnover is worse.

No evidence of AEs was recorded with respect to changes in serum calcium, phosphorus, or intact PTH. No patients were withdrawn from the study because of AEs. A gradual decrease in GFR assessed by creatinine clearance was observed in both the control and treatment groups.

Bisphosphonates. Only one study examined the effect of bisphosphonates in long-term kidney transplant patients with established osteopenia or osteoporosis (Tables 42, 43). Jeffery et al. evaluated 117 patients with reduced BMD (T score <-1). Patients were randomized to daily oral alendronate and calcium vs calcitriol and calcium.⁴⁷¹ There was no untreated control group in this study. One year of therapy was completed by 90 patients. Both treatments showed significant increases in lumbar spine and femur BMD. No differences between groups were shown. No information was provided on the number of patients who did not finish the study. No significant AEs or alterations in kidney function were reported. The quality of evidence of this study was ranked between moderate and low.

In a recent, nonrandomized controlled study by Conley et al., the use of bisphosphonates was retrospectively evaluated in 554 kidney transplant patients who had at least two BMD analyses. Patients who received bisphosphonates after the first year of transplantation showed improved BMD, but did not have a reduced fracture rate when compared with those who did not receive the antiresorptive agents.⁴⁷²

Thus, the Work Group could not make any recommendations for long-term treatment strategies.

SPECIAL CONSIDERATIONS IN CHILDREN

One study reviewed treatments provided to 60 pediatric renal transplant patients (CKD stages 1-5T).⁴⁷³ In this four-arm study (see Table 39), the effect of alfacalcidol+ -calcitonin on BMD, as assessed by DXA, and on selected biochemical markers was compared to that of alendronate. No differences were found. No fracture data were collected. Another 30 patients from the same investigators were given either alfacalcidol or placebo therapy and DXA, and selected biochemistries were assessed.⁴⁷⁴ It is not clear whether these patients were separate from those reported in the first study cited above. Again, there were no differences in outcomes. Given the paucity of data about CKD stages 1-5T, and the inherent inaccuracy in the use of DXA in pediatric CKD, there is insufficient evidence to recommend specific treatments for post-transplant renal bone disease in children at this point in time.

5.7 In patients with CKD stages 4-5T, we suggest that BMD testing not be performed routinely, because BMD does not predict fracture risk as it does in the general population and BMD does not predict the type of kidney transplant bone disease (2B).

In patients with CKD stages 4-5T, there is an increased likelihood of more severe underlying bone abnormalities of CKD-MBD that further decrease the utility of DXA in determining the underlying bone disorder. The data supporting routine use of DXA in a well-functioning allograft are weak (see above), and thus the Work Group felt that the additional confounder of CKD-MBD did not allow a recommendation for routine use of DXA in these patients.

5.8 In patients with CKD stages 4-5T with known low BMD, we suggest management as for patients with CKD stages 4-5 not on dialysis, as detailed in Chapters 4.1 and 4.2 (2C).

Despite not recommending routine DXA in patients with CKD stages 4-5T, the Work Group acknowledged that these patients might still have undergone such an assessment. When the DXA reveals low BMD, the patients should be fully evaluated and managed as for patients without a kidney transplant as detailed in Chapters 4.1 and 4.2. Importantly, these patients should be referred to as having low BMD, as opposed to osteoporosis,⁴⁷⁵ as the latter term often leads to treatments as in the general population with osteoporosis such as bisphosphonates. However, bisphosphonates can decrease bone turnover and therefore may theoretically worsen adynamic bone disease. As detailed in Chapters 3.2 and 4.3, bisphosphonates accumulate in bone for many years, and thus patients should be evaluated with a bone biopsy to ensure normal turnover before their use.

RESEARCH RECOMMENDATIONS

Prospective studies in patients with CKD stages 3-5T should be performed to determine the level of BMD that is predictive of fractures and whether or not the predictive value is affected by other parameters of CKD-MBD, such as HPT.

RCTs should be performed in patients with CKD stages 3-5T with low BMD at the time of kidney transplant to evaluate the effects of bisphosphonates or calcitriol and vitamin D analogs. The study should be of sufficient time (at least 1 year) to evaluate the effect on BMD change and patient-level outcomes, such as hospitalization, fractures, all-cause mortality, cardiovascular morbidity and mortality, and quality of life.

RCTs should be performed in patients with CKD stages 3-5T with low serum calcidiol levels at the time of kidney transplant to evaluate the effect of vitamin D supplementation on change in BMD and patient-level outcomes, such as all-cause mortality, hospitalization, fracture, cardiovascular morbidity and mortality, and quality of life.

SUPPLEMENTARY MATERIAL

Supplementary Table 46. Summary table of RCTs examining treatment of CKD-MBD with calcitriol or vitamin D in CKD stages 1-5T--description of population at baseline.
Supplementary Table 47. Summary table of RCTs examining treatment of CKD-MBD with calcitriol or vitamin D in CKD stages 1-5T--intervention and results.
Supplementary Table 48. Summary table of RCTs examining treatment of CKD-MBD with calcitriol or vitamin D in CKD stages 1-5T--bone biopsy results.
Supplementary Table 49. Adverse events of vitamin D, calcitriol, or vitamin D analogs in CKD stages 1-5T.
Supplementary Table 50. Summary table of RCTs examining treatment of CKD-MBD with bisphosphonates vs control or calcitriol in CKD stages 1-5T--description of population at baseline.
Supplementary Table 51. Summary table of RCTs examining the treatment of CKD-MBD with bisphosphonates vs control or calcitriol in CKD stages 1-5T--intervention and results.
Supplementary Table 52. Summary table of RCTs examining the treatment of CKD-MBD with bisphosphonates vs control or calcitriol in CKD stages 1-5T--bone biopsy results.
Supplementary Table 53. Adverse events of bisphosphonates in CKD stages 1-5T. Supplementary material is linked to the online version of the paper at http://www.nature.com/ki

Supplemental Tables