Adherence to dosing schedule of denosumab therapy for osteoporosis during COVID-19 lockdown: an electronic medical record and pharmacy claims database study from Asia

Summary COVID-19 lockdowns have impacted management of chronic diseases such as osteoporosis. Adherence to the 6-monthly dosing schedule of denosumab, the parenteral anti-osteoporosis medication most often used in Singapore, was significantly reduced during the lockdown period compared to that during pre-COVID-19 times. Patients managed by endocrinologists were more likely to be adherent. Purpose No study thus far has quantified actual adherence rates to anti-osteoporosis therapy with denosumab during COVID-19 or explored factors associated with it. We aimed to estimate the adherence rates to denosumab in Singaporean men and women during COVID-19 lockdown and to compare it with those during the pre-COVID-19 period. Method We conducted this retrospective, electronic medical records, and pharmacy claims database study at Singapore General Hospital, the largest hospital in the country. Patients initiated on subcutaneous denosumab between August 2019 and December 2019 and were thus scheduled to receive the second dose during the COVID-19 first-wave period from February 2020 to June 2020 (lockdown group) were analyzed, as were patients initiated anytime on denosumab between September 2011 and December 2018 (pre-COVID-19 group). Data extracted from the hospital’s electronic prescription platform and patients’ pharmacy purchase records were matched. Adherence was defined as being punctual (with an allowable delay of up to 4 weeks) with the second dose scheduled 6 months from the 1st dose. A sensitivity analysis with an allowable delay up to 8 weeks was also performed. We compared the adherence rates between the two periods and explored factors associated with adherence. Results A total of 768 and 1458 patients respectively during the lockdown and pre-COVID-19 periods were analyzed. The mean adherence rate during lockdown was 63.9%. The odds of being adherent during lockdown were higher if patients were managed by endocrinologists as opposed to those by other specialists [OR 2.516 (95% CI: 1.836–3.448); p