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Recent Advances in
Diagnosis of Tuberculosis
Dr. Muhammad Yahya NooriAssistant Professor
Department of Pathology
DIMC
Focal Person for Provincial Tuberculosis Reference Lab Sindh
DUHS
The Cost
2013
1.5 Million Deaths
9 Million New Cases
Drug Sensitive TB
$100-500/case
MDR TB
$9000-48000/case3
Diagnosis of tuberculosis
Latent Infection Active tuberculosis
Smear examination
Solid and liquid culture
Identification
Susceptibility testing methods
TST
IFN- techniques
Molecular methods
-Detection
-Identification
-Detection of resistance
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Decontamination (in non sterile samples)
Culture in the adequate media
Culture in solid and liquid media
DST
Growth in solid media
Slow: 15d-2mDivision time 18h
Growth in liquid media7-42d
Inoculums!!
Identification Classical and Molecular
methods
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Xpert MTB/RIF Assay
Satisfactory results were obtained in the studies
that were performed in 2010:
• Sensitivity in smear-positive culture-positive specimens:
99%
• Sensitivity in smear-negative culture-positive specimens:
90%
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WHO Evaluation on Xpert MTB/RIF Assay-2011
• Xpert MTB/RIF assay:– Analytical sensitivity: 5 genome copies/purified
DNA
or 131 cfu/ml sputum
(10-100 cfu/ml sputum for culture)
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WHO Evaluation on Xpert MTB/RIF Assay-2011
• Average detection time:– Solid culture: >30 days
– Liquid culture: 17 days
– Microscopy: 1 day
– Xpert MTB/RIF: <1 day
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Xpert MTB/RIF Assay Meta-Analysis Study
• Average sensitivity for detection of rifampicin resistance: 94.1%
• Average specificity for detection of rifampicin resistance: 97.0%
• Average sensitivity in extra-pulmonary specimens: 80.4%
• Average specificity in extra-pulmonary specimens : 86.1%
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