Incidence and Predictors of Repeat Bone Mineral Densitometry: A Longitudinal Cohort Study

Background: Existing guidelines for repeat screening and treatment monitoring intervals regarding the use of dual-energy x-ray absorptiometry (DXA) scans are conflicting or lacking. The Choosing Wisely campaign recommends against repeating DXA scans within 2 years of initial screening. It is unclear how frequently physicians order repeat scans and what clinical factors contribute to their use. Objective: To estimate cumulative incidence and predictors of repeat DXA for screening or treatment monitoring in a regional health system. Design: Retrospective longitudinal cohort study Participants: A total of 5992 women aged 40–84 years who received initial DXA screening from 2006 to 2011 within a regional health system in Sacramento, CA. Main Measures: Two- and five-year cumulative incidence and hazard rations (HR) of repeat DXA by initial screening result (classified into three groups: low or high risk of progression to osteoporosis, or osteoporosis) and whether women were prescribed osteoporosis drugs after initial DXA. Key Results: Among women not treated after initial DXA, 2-year cumulative incidence for low-risk, high-risk, and osteoporotic women was 8.0%, 13.8%, and 19.6%, respectively, increasing to 42.9%, 60.4%, and 57.4% by 5 years after initial screening. For treated women, median time to repeat DXA was over 3 years for all groups. Relative to women with low-risk initial DXA, high-risk initial DXA significantly predicted repeat screening for untreated women [adjusted HR 1.67 (95% CI 1.40–2.00)] but not within the treated group [HR 1.09 (95% CI 0.91–1.30)]. Conclusions: Repeat DXA screening was common in women both at low and high risk of progression to osteoporosis, with a substantial proportion of women receiving repeat scans within 2 years of initial screening. Conversely, only 60% of those at high-risk of progression to osteoporosis were re-screened within 5 years. Interventions are needed to help clinicians make higher-value decisions regarding repeat use of DXA scans.