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Free Content Prolonged positivity of sputum smears with negative cultures during treatment for pulmonary tuberculosis

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SETTING: Acid-fast bacilli (AFB) microscopy of sputum smears is the most widely used tool for both diagnosing pulmonary tuberculosis (PTB) and monitoring treatment response. It is not uncommon for patients who show clinical improvement to have prolonged positivity of sputum smears (i.e., ≥60 days after initiation of treatment) with corresponding negative cultures.

OBJECTIVE: To assess treatment outcomes and characteristics associated with prolonged smear-positive, culture-negative status.

DESIGN: A retrospective review was performed of all patients seen by the Cuyahoga County TB Program in Cleveland from 2000 to 2009. There were 159 consecutive smear-positive, drug-susceptible PTB cases with sufficient analyzable bacteriologic, clinical and radiographic data for study.

RESULTS: A smear-positive, culture-negative pattern was seen in 51 patients (32.1%) ≥2 months after initiation of treatment. Age ≥46 years and extent of baseline chest X-ray abnormality were both significantly associated with a prolonged smear-positive, culture-negative pattern. No patients were culture-positive for Mycobacterium tuberculosis after ≥2 months. There was no increased risk of death in the prolonged smear-positive, culture-negative group, and no confirmed relapses.

CONCLUSION: In our population of patients, in the absence of clinical or radiographic evidence of deterioration, late smear positivity usually has no clinical significance and requires no specific action.
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Keywords: acid-fast bacilli; pulmonary tuberculosis; sputum smear; tuberculosis

Document Type: Research Article

Affiliations: Cuyahoga County Tuberculosis Program, Department of Medicine, Division of Infectious Diseases, Case Western Reserve University–MetroHealth Medical Center, Cleveland, Ohio, USA

Publication date: 2012-12-01

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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.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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