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Sputum microscopy for the diagnosis of HIV-associated pulmonary tuberculosis in Tanzania.

Matee, M., Mtei, L., Lounasvaara, T., Wieland-Alter, W., Waddell, R., Lyimo, J., Bakari, M., Pallangyo, K. and von Reyn, C. F. (2008) Sputum microscopy for the diagnosis of HIV-associated pulmonary tuberculosis in Tanzania. BMC public health, 8. p. 68. ISSN 1471-2458 (In Press)

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In many resource poor settings only sputum microscopy is employed for the diagnosis of HIV-associated pulmonary tuberculosis; sputum culture may not be available. We determined the diagnostic accuracy of sputum microscopy for active case finding of HIV-associated pulmonary tuberculosis using TB culture as the reference standard. 2216 potential subjects screened for a TB vaccine trial submitted 9454 expectorated sputum specimens: 212 (2.2%) were sputum culture positive for Mycobacterium tuberculosis (MTB), 31 (0.3%) for non-tuberculous mycobacteria, and 79 (0.8%) were contaminated. The overall sensitivity of sputum microscopy was 61.8% (131/212) and specificity 99.7% (9108/9132). Sputum microscopy sensitivity varied from 22.6% in specimens with < 20 colony forming units (CFU)/specimen to 94.2% in patients with > 100 CFU/specimen plus confluent growth. The incremental diagnostic value for sputum microscopy was 92.1%, 1.8% and 7.1% for the first, second and third specimens, respectively. The positive predictive value and negative predictive values for sputum microscopy were 84.5% and 99.1%, respectively. The likelihood ratio (LR) of a positive sputum microscopy was 235.1 (95% CI 155.8 - 354.8), while the LR of a negative test was 0.38 (95CI 0.32 - 0.45). The 212 positive sputum cultures for MTB represented 103 patients; sputum microscopy was positive for 57 (55.3%) of 103 patients. Sputum microscopy on 3 expectorated sputum specimens will only detect 55% of culture positive HIV-infected patients in active screening for pulmonary tuberculosis. Sensitivity is higher in patients with greater numbers of CFUs in the sputum. Culture is required for active case finding of HIV- associated pulmonary tuberculosis.

Item Type: Article
Keywords: Sputum Microscopy;HIV;Diagnosis;Pulmonary Tuberculosis;Tanzania
Subjects: HIV > Surveillance
Divisions: Muhimbili University of Health and Allied Sciences (MUHAS)
Depositing User: Mr Joseph Madata
Date Deposited: 27 Nov 2012 05:27
Last Modified: 27 Nov 2012 05:27

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