(B) Impact of the COVID-19 Pandemic on Timeliness of Denosumab Dispensations: An Interrupted Time Series Analysis

Publication Number: 292

Background: Denosumab is an effective semi-annual osteoporosis therapy covered by the Ontario government for residents aged 65 years and older. However, patients are at an increased risk of vertebral fractures shortly after delaying or discontinuing denosumab. Timely administration of denosumab injections every 6 months is thus critical. The COVID-19 pandemic and associated increase in virtual care may have impacted timeliness of denosumab therapy.

Objectives: To estimate the impact of the COVID-19 pandemic on the proportion of older adults who received on-time denosumab dispensations.

Methods: We identified all denosumab dispensations submitted for remuneration to the Ontario government from 2012/02 to 2021/01. For each dispensation between 2015/07 and 2020/06, we calculated the proportion of surviving patients who received an on-time denosumab dispensation 183 +/- 30 days later. Interrupted time series analysis using autoregressive integrated moving average (ARIMA) modeling was used to estimate the impact of the COVID-19 pandemic (starting 2020/03) on the proportion of patients who received on-time denosumab dispensations each month. Models were stratified by: 1) patient residence in community or long-term care (LTC), and 2) user type (first-time user, early user [2-3 prior dispensations], and established user [≥4 prior dispensations]).

Results: We calculated on-time dispensing for 648,221 denosumab claims, 82,561 of which were dispensed in LTC. In the community, the pre-pandemic proportion of on-time dispensations was steady, yet differed across user types (first-time users: ~65%, early users: ~75%, established users: ~80%). We identified an immediate decline in the proportion of on-time dispensations across all user types at the start of the COVID-19 pandemic (-17.8% [95% CI: -19.6, -16.0]), and a 46% monthly increase after April 2020. In LTC, the pre-pandemic proportion of on-time dispensations was higher than in the community and similar across user types (~85%) . We identified a small yet significant decline in the proportion of on-time dispensations at the start of the COVID-19 pandemic (-3.2% [95% CI: -5.0, -1.4]), and a 25% recovery each month after April 2020. The proportion of on-time denosumab dispensations returned to predicted levels by October 2020 in community and LTC.

Conclusions: Timeliness of denosumab dispensations decreased at the start of the COVID-19 pandemic, yet returned to expected levels by Fall 2020. Our findings reveal potential unintended consequences of the COVID-19 pandemic on fracture prevention and warrant future research on fracture rates during the pandemic.