Radiographic Features for Predicting Smear-Negative
Pulmonary Tuberculosis
Nitipatana Chierakul MD*, Jaruwan Boonsuk MD*,
Nisa Muangman MD**, Kanyarat Totanarungroj MD**
Affiliation :
* Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
** Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background : Diagnosis of smear-negative pulmonary tuberculosis (TB) in some circumstances remains a challenge to
physicians especially those working in limited-resource settings.
Objective : To investigate and examine radiographic characters as a predictor of true diagnosis of pulmonary tuberculosis
in patients with negative sputum smears.
Material and Method: This retrospective cross-sectional study was conducted in patients with smear-negative pulmonary
TB at Siriraj Hospital between January 2013 and June 2014. Patients with previous TB treatment, HIV co-infection,
significant pleural effusion, and corticosteroid therapy equivalent to prednisolone greater than 15 mg/day were excluded.
Demographic and clinical data were collected and radiographic features were reviewed and classified as active or inactive
TB by a consensus of three independent reviewers. Various diagnostic parameters for true prediction of TB, as defined by
culture confirmation and/or radiographic improvement, were then examined.
Results : There were 122 patients during the study period, 65 (53%) were male, 27 (22%) were asymptomatic, 20 (16%)
had extrapulmonary involvement, and eight (7%) had concomitant diabetes mellitus. TB was confirmed in 92 patients (75%),
72 had positive culture and 20 had radiographic improvement. Miliary nodules and cavitary lesions had high specificity
(100% and 100%, respectively) and low sensitivity (9.8% and 13%, respectively) for prediction of true TB. Focal interstitial
and alveolar opacities had high positive predictive value (79.5 and 85%) and modest accuracy (62.3 and 47.5%).
Conclusion : Given that specific radiographic features are uncommon and non-specific features are common in smear-negative
pulmonary tuberculosis, clinicians should supplement clinical symptoms, radiological features, and radiological responses
with mycobacterium TB culture to verify diagnosis of TB.
Keywords : Radiographic features, Smear-negative pulmonary tuberculosis
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