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The Importance of AFBMicroscopy in DOTS
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Tuberculosis
A Global Emergency TB kills 5,000 people a day 2-3 million each year
One third of the worlds population is infected with TB
TB kills more young women than any other disease
More than 100,000 children will die needlessly fromTB this year
Hundreds of thousands of children will become TBorphans this year
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TB and AIDS
10%
60%
0%
10%
20%
30%40%
50%
60%
70%
PPD+/HIV-negative PPD+/HIV+
Lifetime Riskof TB
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TB Control:The 5 components of DOTS
TB Register
Political commitment Diagnosis by
microscopy Adequate supply of
SCC drugs Directly observed
treatment Accountability
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Diagnosis of pulmonary tuberculosis
Patients with TB feel ill and seek care promptly
Active case finding is unnecessary andunproductive
Microscopy is appropriate technology, indicatinginfectiousness, risk of death, and priority for
treatment
X-ray is non-specific for TB diagnosis
Serological and amplification technologies (PCR,etc.) currently of no proven value in TB control
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81%
93%100%
0%
50%
100%
First Second Third
Cum
ulativePo
sitivity
Three sputum smearsare optimal
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Diagnosis of Pulmonary TB
Cough 3 weeksAFB X 3
Broad-spectrum antibiotic 10-14 daysIf symptoms persist, repeat AFB smears, X-ray
If consistent with TBAnti-TB Treatment
If 1 positive,X-ray and
evaluation
If 2/3 positive:Anti-TB Rx
If negative:
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98%
70%
0
20
40
60
80
100
AFB Microscopy X-ray
Microscopy is more objectiveand reliable than X-ray
Inter-observer
agreement
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50%
98%
0
20
40
60
80
100
AFB Microscopy X-ray
Microscopy is a more specific
test than X-ray for TB diagnosis
Specificity
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0
20
40
60
80
100
Diagnosed by X-ray alone
Actual cases
X-ray-based evaluation causesover-diagnosis of TB
NTI, Ind J Tuberc, 1974
Over-diagnosis
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Role of Chest X-ray
No chest X-ray pattern is absolutely typical of TB
10-15% of culture-positive TB patients notdiagnosed by X-ray
40% of patients diagnosed as having TB on thebasis of x-ray alone do not have active TB
Toman K. Tuberculosis case finding and chemotherapy. WHO, 1979
X-ray is unreliable for diagnosing and monitoring
treatment of tuberculosis
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Proportion of patients with pulmonaryTB who have positive AFB smears
010203040506070 HIV
NegativeEarly HIV
Late HIV
AFB positivity inTB patients
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DOTS more than doubles accuracy
of diagnosis of TB in SEAR70%
27%
0
10
20
30
4050
60
70
80
Non-DOTS DOTS
%of
caseswithlab
confirmation
Expected range
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Prompt treatment of infectious casesreduces spread of tuberculosis
Smear-positive patients usually seek care
Smear-positive patients are 4-20 times more
infectious Untreated, a smear-positive patient may infect
10-15 persons/year
Smear-positive patients are much more likely todie if untreated
Rouillon A. Tubercle 1976;57:275-99
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DOT prolongs survival ofHIV-infected TB patients
Survived
56.7%
Died
43.3%
SCC with DOTSCC without DOT
Survived
85.4%
Died
14.6%
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Supervision
Effective supervision at all levels is key to success
Supervision is the process of helping staff improve
their performance
Key areas: laboratory work
patient categorization
direct observation
drug storage and stockrecord keeping
reporting