Assessment of sputum smear-positive but culture-negative results among newly diagnosed pulmonary tuberculosis patients in Tanzania
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Date
2017
Journal Title
Journal ISSN
Volume Title
Publisher
Dove Press
Abstract
Diagnosis of pulmonary tuberculosis (TB) in technology-limited countries is widely
achieved by smear microscopy, which has limited sensitivity and specificity. The frequency
and clinical implication of smear-positive but culture-negative among presumptive TB patients
remains unclear. A cross-sectional substudy was conducted which aimed to identify the proportion
of nontuberculous mycobacteria (NTM) infections among 94 “smear-positive culture-negative”
patients diagnosed between January 2013 and June 2016 in selected health facilities in Tanzania.
Out of 94 sputa, 25 (26.60%) were GeneXpert® mycobacteria TB positive and 11/94 (11.70%)
repeat-culture positive; 5 were Capilia TB-Neo positive and confirmed by GenoType MTBC to be
Mycobacterium tuberculosis/Mycobacterium canettii. The remaining 6 Capilia TB-Neo negative
samples were genotyped by GenoType® CM/AS, identifying 3 (3.19%) NTM, 2 Gram positive
bacteria, and 1 isolate testing negative, together, making a total of 6/94 (6.38%) confirmed false
smear-positives. Twenty-eight (29.79%) were confirmed TB cases, while 60 (63.83%) remained
unconfirmed cases. Out of 6 (6.38%) patients who were HIV positive, 2 patients were possibly
coinfected with mycobacteria. The isolation of NTM and other bacteria among smear-positive
culture-negative samples and the presence of over two third of unconfirmed TB cases emphasize
the need of both advanced differential TB diagnostic techniques and good clinical laboratory
practices to avoid unnecessary administration of anti-TB drugs.
Description
Journal article
Keywords
Nontuberculous mycobacteria, Pulmonary TB, Smear-positive, Culture-negative, Tuberculosis diagnosis
Citation
https://doi.org/10.2147/IJGM.S137469