Authors: Tamhane, A.¹; Chheng, P.¹; Dobbs, T.¹; Mak, S.²; Sar, B.³; Kimerling, M.E.⁴

Source: The International Journal of Tuberculosis and Lung Disease, Volume 13, Number 3, March 2009 , pp. 347-354(8)

Publisher: International Union Against Tuberculosis and Lung Disease

Abstract:

DESIGN: Retrospective data analysis of human immunodeficiency virus (HIV) infected patients attending an HIV clinic (referral hospital), Cambodia. Chest X-rays (CXRs) were read independently by onsite and offsite physicians.

RESULTS: Data on 881 patients were analyzed (smear-negative = 776, smear-positive = 105). Overall, the prevalence of culture-confirmed pulmonary tuberculosis (PTB) was 17% (150/881, smear-negative = 62/150). For those with any positive culture, a smear-negative case was four times more likely to be mycobacteria other than tuberculosis (MOTT) than Mycobacterium tuberculosis (P = 0.001). Median CD4 count was higher in smear-negative than smear-positive PTB patients (92.5 vs. 42, P = 0.24). Age, symptoms (cough >3 weeks or hemoptysis or fever >1 month) (aOR 2.6, P = 0.02) and an abnormal CXR (offsite reading) (aOR 4.9, P < 0.001) were significant predictors of smear-negative PTB. CXR was no longer significant in the model using the onsite reading (aOR 1.6, P = 0.11). The combination of age ≥30 years plus symptoms had a sensitivity of 100% but a positive predictive value (PPV) of 9%. CXR (offsite), as the next diagnostic test, had a sensitivity of 50% and specificity of 83%. The sensitivity of smear microscopy was 59% and its specificity 97%.

CONCLUSIONS: While age and symptoms are useful both in screening smear-negative PTB suspects and in predicting smear-negative PTB cases, they have limited PPV. Given the limitations of smear microscopy, culture is required to diagnose smear-negative disease. Where culture is unavailable, CXR is an important adjunct for diagnosis. However, inaccurate CXR interpretation can impact case detection.

Keywords: pulmonary tuberculosis; smear-negative; HIV-infected; predictors

Document Type: Regular paper

Affiliations: 1: Gorgas Tuberculosis Initiative, Division of Infectious Diseases, Department of Medicine, The University of Alabama at Birmingham, Birmingham, Alabama, USA 2: Provincial Hospital, Provincial Health Department, Battambang, Cambodia 3: Institute Pasteur du Cambodge, Phnom Penh, Cambodia 4: Gorgas Tuberculosis Initiative, Division of Infectious Diseases, Department of Medicine, The University of Alabama at Birmingham, Birmingham, Alabama, USA; and Global Health Program, Bill and Melinda Gates Foundation, Seattle, Washington, USA

Publication date: 2009-03-01

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• The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

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