Ajay K. Singh, MBBS, FRCP, MBA
Brigham and Women’s Hospital and Harvard Medical School
Fractures in chronic kidney disease (CKD) patients, particularly those that are elderly, have substantial morbidity and mortality. The Kidney Disease Improving Global Outcomes 2017 Clinical Practice Guideline Update for the Diagnosis, Evaluation, Prevention, and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder (KDIGO CKD-MBD)1, published in July 2017, has provided an important update over the previous 2009 guidelines in one major area—osteoporosis and fracture risk.
For patients in CKD stages G3a (glomerular filtration rate [GFR] of 45-59 ml/min/1.73m2) to G5D (patients on dialysis), the newly updated guideline 3.21 states, “We suggest BMD [bone mineral density] testing to assess fracture risk if results will impact treatment decisions [2B].” In the 2009 guideline [3.2.2], the KDIGO-MBD workgroup had recommended against routine BMD testing “because BMD does not predict fracture risk as it does in the general population, and BMD does not predict the type of renal osteodystrophy [2B].” The new update documents multiple new prospective studies and post hoc analyses from clinical trials. Furthermore, in the newly updated guideline, the KDIGO Work Group voted to remove the requirement of bone biopsy prior to the use of anti-resorptive therapy for osteoporosis.
Published data from 2009 onwards reveal three salient points:
- Lower total hip and femoral neck BMD using dual-energy X-ray absorptiometry (DXA) predicts fractures in patients with CKD stage 3a to stage 5D patients.
- Osteoporosis anti-resorptive medications have similar efficacy on improving BMD and reducing fracture incidence in patients with CKD stage 3a, compared with those with normal or near normal eGFR.
- Evidence is lacking on whether DXA in children and adolescents predicts fractures.
Performing a DXA is pretty straightforward. The more challenging question is: what should one do for a low BMD?
The approach I plan to use is as follows:
- Routinely perform DXA in patients with CKD Stage 3a-5D
- Assess fracture risk with the Canadian WHO fracture risk assessment (FRAX®) tool (https://www.sheffield.ac.uk/FRAX/tool.jsp). Fraser and colleagues2 report “FRAX with BMD showed better fracture discrimination than FRAX without BMD or BMD alone.”
- In most CKD patients with a low or declining BMD, begin anti-resorptive therapy and monitor the patient with serial DXAs3. Of note, the 2017 Update does not require a bone biopsy before beginning anti-resorptive therapy.
- Consider performing a bone biopsy in patients who have either not improved their BMD score despite therapy, have refractory hypercalcemia, or have sustained an unexpected fracture. The bone biopsy should be performed with the goal of demonstrating on quantitative bone histomorphometry low trabecular bone volume and disrupted microarchitecture.
- http://kdigo.org/wp-content/uploads/2017/02/2017-KDIGO-CKD-MBD-GL-Update.pdf Accessed August 21, 2017
- Fraser LA, Langsetmo L, Berger C, et al. Fracture prediction and calibration of a Canadian FRAX® tool: a population-based report from CaMos. Osteoporos Int. 2011 Mar;22(3):829-37. doi: 10.1007/s00198-010-1465-1. Epub 2010 Dec 16.
- Iimori S, Mori Y, Akita W, et al. Diagnostic usefulness of bone mineral density and biochemical markers of bone turnover in predicting fracture in CKD stage 5D patients—a single-center cohort study. Nephrol Dial Transplant. 2012;27:345–351.