INTRODUÇÃO: Early detection of altered bone mineral density (BMD) is important for monitoring bone health status in Cystic Fibrosis (CF) patients. Dual energy X-ray absorptiometry (DXA) is currently the standard method. However, other methods as chest computed tomography (CCT) may be useful to evaluate BMD.
OBJETIVO: The purpose of this study is to determine the accuracy of CTT Hounsfield Units at the thoracic vertebrae to estimate BMD using DXA at the lumbar vertebrae as a gold standard for patients with CF.
METODOLOGIA: This is a retrospective cross-sectional study. All CF patients with chest CT and DXA scans, treated at CF outpatient clinics in two centers in Brazil were included. Bone mineral density was evaluated by thoracic CT (measured by HU) and lumbar DXA (measured by g/cm2). Thoracic CTs were performed using a scanner CT multislice routinely used according to the hospital protocol. We measured the HU in three consecutive thoracic (T10- T12) using the region of interest placed at the center of the vertebrae. DXA scans are routinely performed with Hologic Discovery densitometer. Information from the dual x-ray absorptiometry scans, including z-scores and BMD (measured in g/cm2), was obtained for the first through fourth lumbar vertebrae.
RESULTADOS: A total of 73 CF patients were evaluated. Patients with DXA-defined osteoporosis showed significantly lower HU values. Using 215HU as cut-off, we found 83% sensitive and 68% specific for osteoporosis in this group. ROC area under the curve was 0.86 using T10-T12 level assessed.
CONCLUSÃO: Our study suggests that opportunistic measurement of bone attenuation using low-dose chest CT has acceptable sensitivity/specificity comparable to DXA. More importantly, such an approach may be an option for patients that already need a chest CT for other purposes. The paradigm of using CTs obtained for other reasons to opportunistically screen for osteoporosis promises to substantially improve patient care.
