Judging respiratory specimen acceptability for AFB microscopy: visual vs. microscopic screening

To investigate whether visual assessment or microscopic grading of the cellular composition of specimens is a better strategy to screen specimen quality for tuberculosis (TB) diagnosis. About 2643 specimens were collected from TB suspects at the Federal TB centre in Pakistan. Specimens were classifi...

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Bibliographic Details
Published in:Tropical medicine & international health 2009-05, Vol.14 (5), p.571-575
Main Authors: Khan, Mishal S, Dar, Osman, Tahseen, Sabira, Godfrey-Faussett, Peter
Format: Article
Language:English
Subjects:
Bacteria
Bacterial diseases
Biological and medical sciences
Culture Media
diagnosis
diagnostic
Diagnostic tests
diagnóstico
General aspects
Human bacterial diseases
Humans
Infectious diseases
Medical sciences
Microscopy
Microscopy - methods
Pakistan
Pakistán
Practice Guidelines as Topic
Quality
Reproducibility of Results
Saliva - microbiology
Samples
Specimen Handling
Sputum - microbiology
tuberculose
Tuberculosis
Tuberculosis and atypical mycobacterial infections
Tuberculosis, Pulmonary - diagnosis
Tuberculosis, Pulmonary - microbiology
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Summary:To investigate whether visual assessment or microscopic grading of the cellular composition of specimens is a better strategy to screen specimen quality for tuberculosis (TB) diagnosis. About 2643 specimens were collected from TB suspects at the Federal TB centre in Pakistan. Specimens were classified as sputum or saliva visually and microscopically using the criteria proposed by McCarter and Robinson, Van Scoy, Geckler et al., Murray and Washington and Bartlett. The acid-fast bacilli (AFB)-positivity of specimens was also assessed. Despite being the least 'technical' and time consuming, visual assessment rejected the lowest proportion of AFB-positive specimens (0.3%). Most microscopic grading criteria, particularly those that considered the squamous epithelial cell count, rejected a large proportion of specimens (30-66%), of which a sizeable fraction contained AFB (6-12%). Our results indicate that visual assessment by trained technicians is more effective and suitable than microscopic grading for screening specimens for TB diagnosis. TB control resources could be better allocated to optimizing visual screening than investing in more 'strict' microscopic grading tools.
ISSN:1360-2276
1365-3156
DOI:10.1111/j.1365-3156.2009.02260.x