Tuberculosis, Genexpert Recommendations

1. Diagnostics of Tuberculosis
An insight into Gene Expert
Dr. Muhammad Yahya Noori
Assistant Professor
Department of Pathology
Focal Person for Provincial Tuberculosis
Reference Lab Sindh
DIMC
DUHS

2. Tuberculosis
Second only to HIV/AIDS
One in three humans carries the Bacilli
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3. The Cost
2013
1.5 Million Deaths
9 Million New Cases
Drug Sensitive TB
$100-500/case
MDR TB
$9000-48000/case
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4. Pakistan
Burden of Disease
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5. Pakistan
New Cases
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6. 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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7. 7

8. finddiadnostics.org

9. Example of Rif-Sensitive Profile – 5 probes are
positive
MTB/Rif Assay design
Molecular
Beacon
Target
Hybrid
Each probe is labeled with a different fluorophore,
permitting simultaneous detection of the presence
of wild type.
The MTB assay target is the 81 bp region (RRDR) of the rpoB gene.
SPC
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10. 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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11. 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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12. 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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13. Processing
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14. 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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15. Current Practices
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16. All smear Positive new
treatment cases that remain +ve
two months after treatment
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17. All Hospitalized patients who
have presumptive TB
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18. Presumptive smear negative
cases at high volume centers
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19. Health care workers with TB
symptoms
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20. First line treatment failures
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21. MDR-TB contacts
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22. TB/HIV
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23. History of ATT
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24. Thank you
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