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Morphologic Predictors of a Microbiological Yield in Patients With a Tree-in-Bud Pattern on Computed Tomography

Desai, Sujal R. MD, FRCP, FRCR; Edey, Anthony J. MRCP, FRCR; Hansell, David M. MD, FRCP, FRCR; Shah, Aarti MRCP, FRCR; Land, David MRCP; Arnott, Sarah MRCPath; Barker, Richard D. MD, MRCP; Wells, Athol U. MD, FRACP, FRCR (Hon)

doi: 10.1097/RTI.0000000000000078
Original Articles

Purpose: To evaluate the computed tomographic (CT) predictors of a clinically significant yield from microbiological tests in patients with a tree-in-bud pattern.

Materials and Methods: CT examinations in 53 patients (male=34; mean age=52.9±17.3 y) with a tree-in-bud pattern in whom a diagnostic test (sputum analysis, bronchoalveolar lavage or nasopharyngeal aspirates) had been performed within 2 weeks were identified. The following CT patterns were independently quantified by 2 thoracic radiologists: tree-in-bud, bronchiectasis, bronchial wall thickening, consolidation, ground-glass opacification, and nodules. The presence of cavitation (in nodules and/or consolidation) was recorded. Patient charts were reviewed for the presence of a clinically significant positive microbiological result.

Results: A clinically significant causal organism was present in 25/53 (47%) patients. The median extent of a tree-in-bud pattern was 5 [range=1 to 16 (maximum range=0 to 18)], and cavitation was present in 14/53 (26%) patients (cavitating nodules=8, cavitation in consolidation=3, and cavitation in consolidation and nodules=3). There was no independent linkage between the extent of a tree-in-bud pattern and the identification of a clinically significant organism. The microbiological yield was significantly higher if there was coexistent cavitation in nodules or consolidation [11/14 (79%) vs. 14/39 (39%); P=0.005]. On stepwise logistic regression, the only CT predictor of a clinically significant microbiological yield was cavitation on CT (odds ratio=9.7; 95% confidence interval=1.9, 49.9; P<0.01); the extent of a tree-in-bud pattern, concurrent use of antibiotics, age, and sex were not independently linked to a significant microbiological yield.

Conclusions: A specific clinically significant microbiological diagnosis was obtained in approximately 50% of patients with a tree-in-bud pattern. The microbiological yield rises strikingly when a tree-in-bud pattern coexists with cavitation (in nodules or consolidation) but is not predicted by ancillary CT signs or clinical parameters.

Departments of *Radiology

Respiratory Medicine

§Haemato-Oncological Medicine, King’s College Hospital

Department of Radiology

Interstitial Lung Disease Unit, Royal Brompton Hospital, London, UK

The authors declare no conflicts of interest.

Reprints: Sujal R. Desai, MD, FRCP, FRCR, Department of Radiology, King’s College Hospital Foundation NHS Trust, Denmark Hill, London SE5 9RS, UK (e-mail:

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