AFB Microscopy in DOTS (Day 2)

7/31/2019 AFB Microscopy in DOTS (Day 2)

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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

Documents

AFB Microscopy in DOTS (Day 2)