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

Abstract

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.

Keywords: medical decision-making; osteoporosis; practice variation; screening.

Figure 1

Cumulative incidence of repeat bone densitometry (DXA) for women not placed on osteoporosis drug* after initial DXA, by initial DXA result. *Drugs classified as osteoporosis drugs included bisphosphonates, raloxifene, teriparatide, calcitonin, and denosumab, but not estrogens, calcium, or vitamin D. ^aLow risk on initial DXA is defined as normal at all sites (T-score ≥ −1.0), mild osteopenia (−2.0 < T-score < −1.0) at the femoral neck or anterior-posterior spine, or any osteopenia at other sites (−2.5 < T-score < −1.0). ^bHigh risk on initial DXA is defined as advanced mainsite osteopenia (−2.5 < T-score < −2.0) or non-mainsite osteoporosis (T-score ≤ −2.5). ^cOsteoporosis on initial DXA is defined as mainsite T-score ≤ −2.5.

Figure 2

Cumulative incidence of repeat bone densitometry (DXA) for women placed on osteoporosis drug* after initial DXA, by initial DXA result. *Drugs classified as osteoporosis drugs included bisphosphonates, raloxifene, teriparatide, calcitonin, and denosumab, but not estrogens, calcium, or vitamin D. ^aLow risk on initial DXA is defined as normal at all sites (T-score ≥ −1.0), mild osteopenia (−2.0 < T-score < −1.0) at the femoral neck or anterior-posterior spine, or any osteopenia at other sites (−2.5 < T-score < −1.0). ^bHigh risk on initial DXA is defined as advanced mainsite osteopenia (−2.5 < T-score < −2.0) or non-mainsite osteoporosis (T-score ≤ −2.5). ^cOsteoporosis on initial DXA is defined as mainsite T-score ≤ −2.5.