Retrospective analysis of eligibility for denosumab in patients presenting with osteoporotic fractures and renal impairment treated by orthogeriatric service at Middlemore Hospital.

BACKGROUND

Little is known about the prevalence of renal impairment in patients presenting with osteoporotic fractures contraindicating bisphosphonate use in New Zealand, and their eligibility to denosumab.

AIM

To assess the prevalence of renal impairment contraindicating bisphosphonate use in older adults presenting with osteoporotic fractures, differences in demographic variables between those with renal impairment and those who do not, and finally to assess eligibility for denosumab based on the current PHARMAC special authority criteria.

METHOD

All patients 65 years and older with osteoporotic fractures treated by inpatient orthogeriatric service (IOS) and the outpatient fracture liaison service (FLS) at Middlemore Hospital between 1 February to 31 April 2019 were assessed. Following data was retrospectively collected-age, sex, ethnicity, preadmission residential status, type of acute osteoporotic fractures, history of previous osteoporotic fractures, cognitive impairment and its severity, history of falls, previous dual-energy x-ray absorptiometry (DEXA) scan and the worst documented T-scores over total hip, neck of femur or L1-4 spine and previous funded anti-resorptive therapy use. Creatinine clearance (CrCl) was calculated using the Cockcroft-Gault formula based on the ideal body weight according to the recorded height and serum creatinine level at the time of patient's presentation. Patients with CrCl below 35ml/min were assigned to the renal group, and those with CrCl above 35ml/min to the non-renal group. Current PHARMAC criteria for denosumab was used to assess the eligibility in the renal group.

RESULTS

Total of 190 patients (102 IOS and 88 FLS) were assessed. Thirty-four patients (17.9%) had renal impairment with CrCl less than 35ml/min and were assigned to the renal group. There were no statistically significant differences in demographic variables between the renal and the non-renal group other than for age, where the renal group was significantly older (85.4 vs 77.5 years, P-value <0.0001). Two out of 34 patients were eligible for denosumab. Reasons for ineligibility to denosumab were as follows; not meeting the definition of severe established osteoporosis due to presenting with their first ever osteoporotic fracture (64.7%), no previous DEXA scans to quantify their bone mineral density (11.8%), measured bone mineral density T-score above -2.5 (5.9%); and no preceding treatment with a funded anti-resorptive therapy for at least 12 months prior to their osteoporotic fracture (11.8%).

CONCLUSION

Considerable number of patients aged 65 years and older with osteoporotic fractures also had renal impairment contraindicating the use of bisphosphonates. There were no significant differences in demographic variables between the renal and non-renal group other than for age. Majority of patients in the renal group were ineligible for denosumab based on the current special authority criteria. These results highlight the need for further review and revision of the current PHARMAC criteria to improve access to denosumab in older adults with renal impairment and osteoporotic fractures.

Déclaration de conflit d'intérêts

Nil.