Clinical utility of abnormal opacity overlying the vertebral column on lateral chest radiography

Chest radiography is an important component of the evaluation of patients with complaints referable to the chest. We sought to investigate the clinical utility of one particular finding on the lateral chest radiograph (CXR), namely, radioopacity obscuring the normal superior to inferior progression of vertebral radiolucency. A review of the literature yielded little published evidence to characterize the clinical utility of this finding to date.

We retrospectively identified 370 patients from a hospital database who underwent both computed tomography (CT) imaging of the chest and lateral chest radiography within 24 hours. We calculated the sensitivity, specificity, and likelihood ratios (LRs) associated with the presence or absence of an abnormal opacity overlying the vertebral column on lateral chest radiography using CT imaging of the chest as the reference standard. We also estimated interobserver and intraobserver reliability of this finding.

Abnormal opacity overlying the vertebral column had a sensitivity of 86.9% (95% confidence interval [CI], 82.5%-90.3%) and specificity of 70.4% (95% CI, 59.7%-79.2%) for relevant CT-documented lower lobe and associated structural pathology. The associated summary positive LR (LR+) was 2.9 (95% CI, 2.1-4.1) and summary negative LR (LR-) was 0.19 (95% CI, 0.13-0.26). Kappa statistics were indicative of moderate intraobserver and interobserver agreement.

The presence of abnormal opacity overlying the vertebral column on lateral chest radiography increases the probability of lower lobe and associated structural pathology somewhat. The absence of this finding decreased the probability of such pathology to a greater degree. Thus, this finding is useful in differentiating those patients with pathology from those without.