Opportunistic screening of osteoporosis in lung transplant recipients: diagnostic value of pre-transplant thoracic CT using vertebral Hounsfield units.

Purpose: To evaluate the diagnostic performance of pre-transplant chest computed tomography (CT) as an opportunistic screening tool for predicting osteoporosis 1 year after lung transplantation.

Method: We retrospectively enrolled lung transplant patients from a tertiary center in Zhejiang, China, between September 2022 and December 2023. Standardized regions of interest were placed on the first thoracic vertebra (T1) through the first lumbar vertebra (L1) to measure CT-derived Hounsfield unit (HU) values. Patients were categorized into normal BMD, osteopenia, and osteoporosis groups on the basis of their baseline dual-energy X-ray absorptiometry (DEXA) T-scores. Clinical baseline characteristics and HU values were compared among the three groups. The correlation between pre-transplant HU values and DEXA T-scores was analyzed, and receiver operating characteristic (ROC) curves were used to assess the diagnostic performance of pre-transplant HU values in predicting post-transplant osteopenia and osteoporosis.

Results: A total of 139 lung transplant patients were included in the study, among whom 60 had normal bone mass, 51 had osteopenia, and 28 had osteoporosis at baseline. Notably, HU values significantly differed among the three groups (P < 0.05). The HU values of T1-L1 were weakly to moderately positively correlated with the T-scores of the lumbar spine (LS), femoral neck (FN), and total hip (TH; r = 0.28-0.51, P < 0.01). After lung transplantation, the proportion of patients with low bone mineral density (BMD) increased, and T-scores of the FN and TH decreased (P < 0.01). Baseline HU values showed good diagnostic performance for detecting bone abnormalities 1 year after transplantation, with T2 showing particular potential for distinguishing osteoporosis from non-osteoporosis and T9 for distinguishing low BMD from normal BMD.

Conclusions: Pretransplant thoracic CT provides a clinically feasible and opportunistic screening approach to stratify osteoporosis risk in lung transplant candidates without additional radiation exposure. By quantifying T2 and T9 vertebral HU values, clinicians can identify high-risk patients for timely intervention, potentially reducing fracture-related morbidity.