Introduction: Transbronchial lung biopsy (TBB) has a variable diagnostic yield in sarcoidosis. We hypothesised that the extent and pattern of parenchymal disease on CT would predict the likelihood of a positive TBB.
Methods: Patients with sarcoidosis (n=77) were included if they had CT within 6 weeks of TBB. Ethnicity, symptoms, pulmonary function, and site and results of TBB and bronchoalveolar lavage (BAL) were recorded. CT scans were scored quantitatively for patterns of parenchymal disease (nodular, reticular, consolidation and ground glass) on a lobar basis.
Results: Thirty nine (50.6%) patients had a positive TBB. Symptoms, ethnicity, treatment, lung volumes and CXR stage were not predictors of a positive biopsy. Female gender (p<0.01), reduced %predicted DLCO (p=0.04) and higher BAL %lymphocytes (p=0.05) were associated with positive biopsy, as were higher total lung score (p=0.02), reticular pattern (p=0.01) and ground glass opacity (p=0.04). The associations were more significant for the total lobar score (p=0.01), and lobar ground glass score (p=0.03) of the lobe biopsied. On multivariate analysis gender, BAL % lymphocytes and total lung score were independent predictors of a positive TBB.
Conclusion: The total extent of parenchymal disease on CT scan in addition to the pattern and lobar distribution predicts the likelihood of a positive TBB at bronchoscopy.