B45-13 Prevalence and Correlates of Low Bone Mineral Density Among People With Cystic Fibrosis in an Adult Cystic Fibrosis Center

Rationale Low bone mineral density (BMD) is a well-established comorbidity in people with cystic fibrosis (CF). We quantified BMD categories and described clinical correlates (sex, age, BMI, vitamin D levels, modulator use, cystic fibrosis-related diabetes mellitus (CFRD), pancreatic insufficiency, and transplant history) in a single-center cohort. Methods We performed a single-center retrospective review of current CF patients (N = 191) evaluated at the Adult Cystic Fibrosis Center at Inova Fairfax. Patients with at least 1 dual-energy X-ray absorptiometry (DEXA) scan were analyzed (n = 135) and sub-categorized by T/Z-score: osteoporosis (≤-2.0), osteopenia (-1.0 to -2.0), normal (≥-1.0) per CF Foundation guidelines. We further analyzed differences in sex, age, BMI, vitamin D levels (pre/post DEXA), modulator use/type, CFRD, pancreatic insufficiency, transplant history, and the lowest T/Z score sites on DEXA. Results Among 191 CF patients, 135 had at least 1 DEXA scan performed. 45 patients had osteoporosis (33.3%), 46 had osteopenia (34.1%), and 44 had normal BMD (32.6%). Sex was balanced across strata (M-F): 24-21(osteoporosis)/28-18(osteopenia)/23-21(normal). Mean age decreased with better BMD (years): 42.7/38.7/30.6. Mean BMI increased with better BMD (kg·m-2): 22.7/24.3/26.4. Vitamin D change did not demonstrate a clear trend across strata (ng/mL): 39.1-pre; 39.4-post/33.3-pre; 32.6-post/34.8-pre; 36.4-post. Modulator use (n = 93) was increased in patients with better BMD: 31.1%/32.3%/36.6%; Elexacaftor/tezacaftor/ivacaftor accounted for 88/93 patients, Ivacaftor 4/93, and Lumacaftor-ivacaftor 1/93. BMD appeared similar in patients with CFRD (n = 51) versus patients without CFRD (n = 84): 35.3%/35.3%/29.4% versus 32.1%/33.3%/34.5%. The presence of pancreatic insufficiency (n = 102) versus pancreatic sufficiency (n = 33) demonstrated an opposite trend toward better BMD: 32.4%/33.3%/34.3% versus 36.3%/36.3%/27.3%. In patients with a history of transplant (n = 14), their post-transplant DEXA correlated with lower BMD: 71.4%/14.3%/14.3%. When reviewing the lowest T/Z score sites, these were found at the following locations: spine 54, left femur 49, right femur 5, left hip 8, right hip 0, left forearm 5, whole body 4, multiple 7, unspecified 1. Conclusion In this single-center CF cohort, approximately two-thirds of DEXA-scanned CF patients had low BMD (osteoporosis or osteopenia). Lower mean age, higher mean BMI, and higher modulator use aligned with higher BMD, whereas antecedent transplantation was associated with lower BMD, consistent with compounded effects of advanced disease and immunosuppression. CFRD and pancreatic insufficiency were prevalent but showed only modest cross-sectional gradients. Vitamin D levels showed no consistent cross-sectional gradient. These data support routine bone-health surveillance and motivate adjusted analyses to identify independent, modifiable risk factors in people with CF.