Download - Tb Dots Module1

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Module 1 Understanding Tuberculosis,

the Global Emergency

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Learning Objectives At the end of this module, the participant will be able to:

1. Explain the TB epidemic and the annual global

TB burden

2. Describe the forms of TB and how TB is

transmitted

3. Discuss the ISTC Standards for Diagnosis

4. Define and compare various methods of TB

diagnosis,

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Learning Objectives

5. Describe NTP and its purposes

6. Describe the role of the laboratory in NTP

7. Describe the DOTS component of STOP TB

strategy

8. Explain the importance of AFB microscopy in

the DOTS program

9. Describe levels of TB laboratory services.

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Content Overview • What is tuberculosis?

• The TB epidemic and the annual global TB burden

• Transmission and forms of TB

• Risk of Disease

• ISTC Standards for Diagnosis

• TB Diagnosis

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• National TB Program and its purposes

• The role of the laboratory in NTP

• The DOTS component of STOP TB strategy

• The importance of AFB-microscopy in DOTS

programs

• Levels of laboratory services

Content Overview

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Global Emergency

Tuberculosis kills 5,000 people a

day !

2.3 million die each year !

Source: http://wwwn.cdc.gov/dls/ila/acidfasttraining/section4.aspx

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• 1/3 of world’s population is infected with TB

• 8 Million people develop active TB every year

• TB kills more young women than any other

disease

• More than 100,000 children will die from TB

this year

• Hundreds of thousands of children will become

TB orphans

Disturbing Statistics


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PHILIPPINE STATUS

9th amongst the 22 high-burdened countries worldwide (WHO watchlist)

4th amongst the countries in the Western Pacific Region of WHO

(2nd among the HBC’s in WPRO)

8th amongst the countries with high burden for MDRTB

TB is 6th in mortality and morbidity

TB morbidity & mortality Nat’l Objectives for Health 2005-2010 DOH

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What is TB?

TB is an infectious disease that affects

mainly the lungs (pulmonary TB or PTB)

but can also attack any part of the body

(extra-pulmonary TB or EPTB)

A person with

PTB is infectious to others!


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Mycobacterium tuberculosis complex

• Mycobacterium tuberculosis

• Mycobacterium bovis

The Causes of TB


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Staining Characteristics

• Mycobacteria are called Acid-Fast Bacilli (AFB) due to their microscopic appearance after decolorization.

• Organisms appear red on a blue background


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TB Transmission

(infection)

Person to person

via

Airborne transmission

in

Confined environment


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• Exposure to TB bacilli

• Duration of exposure to a person with PTB

• Intensity of exposure

• Untreated AFB smear positive PTB

cases are the most infectious

Risk Factors for Infection


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Risk Factors for Disease

• Development of disease depends on individual susceptibility

• HIV increases the risk of getting TB disease

10% Life time risk of TB in HIV negative

10% Annual risk of TB in HIV positive


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What is MDR-TB?

• Multidrug-resistant TB (MDR TB) is TB that is

resistant to at least two of the best anti-TB

drugs, isoniazid and rifampicin. These drugs

are considered first-line drugs and are used to

treat all persons with TB disease.

ISTC TB Training Modules 2009

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What is XDR-TB?

• Extensively drug resistant TB (XDR TB) is a

relatively rare type of MDR TB. XDR TB is

defined as TB which is resistant to isoniazid

and rifampin, plus resistant to any

fluoroquinolone and at least one of three

injectable second-line drugs (i.e., amikacin,

kanamycin, or capreomycin).


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Purpose of ISTC Purpose of ISTC


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THE ISTC

Intended to facilitate the effective engagement of all care providers in delivering high quality care for patients of all ages.

… intended to complement, not replace, national and local recommendations.

The ISTC should be viewed as a living document that will be revised as technology, resources, and circumstances change.

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Introduction


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Standards for Diagnosis



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Standards for Diagnosis


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Microbiologic Diagnosis of TB

Significance of microbiologic testing for public health goals and patient care:

WHO global target of 70% case detection of new smear-positive cases

Rapid and accurate case detection coupled with effective treatment is essential to reduce the incidence of TB

Failure to perform a proper diagnostic evaluation before initiating treatment potentially:

• Exposes the patient to the risks of unnecessary or wrong treatment

• May delay accurate diagnosis and proper treatment

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ISTC Standard 1

All persons with

otherwise

unexplained

productive cough

lasting two-three

weeks or more

should be

evaluated for

tuberculosis

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ISTC Standard 2 All patients (adults, adolescents, and children who are capable of producing sputum) suspected of having pulmonary TB should have at least two sputum specimens obtained for microscopic examination in a quality-assured laboratory. When possible, at least one early morning specimen should be obtained.

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ISTC Standard 3

For all patients (adults, adolescents, and children) suspected of having extrapulmonary TB, appropriate specimens from the suspected sites of involvement should be obtained for microscopy, culture, and histopathological examination.

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NTP Extra-Pulmonary TB (EP)

• A patient with at least one mycobacterial smear/culture positive from an extra-pulmonary site (organs other than the lungs: pleura, lymph nodes, genito-urinary tract, skin, joints and bones, meninges, intestines, peritoneum, and pericardium, among others)

• A patient with histological and/or clinical evidence consistent with active extra pulmonary TB and there is a decision by a physician to treat the patient with anti-TB drugs

• All EP cases shall undergo DSSM prior to treatment.

NTP MOP 2005

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ISTC Standard 4

All persons with chest

radiographic findings

suggestive of

tuberculosis should

have sputum

specimens submitted

for microbiological

examination.

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ISTC Standard 5 The diagnosis of sputum smear-negative pulmonary

tuberculosis should be based on the following criteria:

• At least two negative sputum smears (including at least one early morning specimen)

• Chest radiography findings consistent with tuberculosis

• Lack of response to a trial of broad-spectrum antimicrobial agents

• (Note: Because the fluoroquinolones are active against M. tuberculosis complex, and thus may cause transient improvement in persons with tuberculosis, they should be avoided.)

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ISTC Standard 5

For such patients, sputum cultures should be obtained. In persons who are seriously ill or have known or suspected HIV infection, the diagnostic evaluation should be expedited and if clinical evidence strongly suggests TB, a course of antituberculosis treatment should be initiated.


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ISTC Standard 6

In all children suspected of having intrathoracic (i.e., pulmonary, pleural, and mediastinal or hilar lymph node) TB, bacteriological confirmation should be sought through examination of sputum (by expectoration, gastric washings, or induced sputum) for smear microscopy and culture.

In the event of negative bacteriological results, a diagnosis of TB should be based on:

The presence of abnormalities consistent with TB on chest radiography

A history of exposure to an infectious case, evidence of TB infection (positive tuberculin skin test or interferon gamma-release assay), and

Clinical findings suggestive of TB

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ISTC Standard 6

For children suspected of

having EPTB, appropriate

specimens from the

suspected sites of

involvement should be

obtained for microscopy

and for culture and

histopathological

examination.

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Diagnosis of TB

• Direct demonstration of AFB in sample

• Growth of TB bacilli in culture

• Skin Test

• Nucleic Acid Amplification tests

(NAATs)

• T-cell-based interferon-gamma release

assay (IGRAs)

• X-Ray


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Sputum Smear Microscopy • Sputum smear microscopy is the

most important test for the

diagnosis of pulmonary TB in many

areas of the world

• Direct smears (unconcentrated

specimen) are most common

• Fluorescence microscopy and

chemical processing can increase

sensitivity

• Assessment of laboratory quality is

essential


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Sputum Microscopy: Direct Smears

Direct smears of

unconcentrated sputum:

Fast, simple, inexpensive,

widely applicable

Extremely specific for

M. tuberculosis in

high-incidence areas

Ziehl-Neelsen staining

(carbol fuchsin type) most

common


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Sputum Smear Microscopy

Carbolfuchsin-based stains

• Utilize a regular light microscope

• Must be read at a higher magnification

• Two types: Ziehl-Neelsen and Kinyoun. Both use

carbolfuchsin/phenol as the primary dye

• Smear is then decolorized with acid (HCI) alcohol and

counter-stained with methylene blue


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Ziehl-Neelsen (ZN) Stain


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Sputum Microscopy: Fluorochrome Stain

Fluorochrome stain

• Fluorochrome stained smears require a fluorescent

microscope

• Generally read at 250X-450X magnification which

allows rapid scanning of the smear

• Auramine-rhodamine is an example of such a stain

where the AFB appear yellow against a black

background


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Auramine-rhodamine Stain


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Advantages of

AFB Smear Microscopy

• Microscopy is a simple convenient test

• Requires minimal infrastructure and equipment

• Highly accurate, inexpensive and fast

• Accessible to the majority of patients

• Prioritizes infectious cases


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Limitations of Microscopy

• Can not distinguish between dead or live bacteria

• High bacterial load >3000–5000 AFB /mL is required for detection

• Can not do species identification

• Can not perform Drug Susceptibility Testing


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Fluorescence Microscopy

Advantages:

• More accurate: 10% more sensitive

than light microscopy, with specificity

comparable to ZN staining

• Faster to examine = less technician

time

Disadvantages:

• Higher cost and technical complexity,

less feasible in many areas

Steingart KR, et al. Lancet Infect. Dis. 2006; 6 (9):570-81

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Although sputum

microscopy is the first

bacteriologic diagnostic

test of choice, both culture

and drug susceptibility

testing (DST) can offer

significant advantages in

the diagnosis and

management of TB.

Culture and Drug Susceptibility Testing


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Culture: Advantages

• Higher sensitivity than smear microscopy (culture

can make diagnosis despite fewer bacilli in

specimen)

• If TB suspected and sputum smears are negative,

culture may provide diagnosis

• Allows for identification of mycobacterial species

• Allows for drug susceptibility testing


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Culture: Disadvantages

• Cost

• Technical complexity

• May take weeks to get results

• Requires ongoing quality assurance

Therefore, more likely to be found in major

referral centers. Avoid delaying appropriate TB

treatment in suspicious cases while awaiting

results.


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Culture: Solid Media

• Solid media have the

advantage that organisms

(colonies) can be seen on the

surface of the medium

• Types most commonly used

are:

• Lowenstein-Jensen:

egg-based

• Middlebrook 7H 10 or 7H11:

agar-based

• Ogawa


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MGIT Incubator

Culture: Liquid Media

• More sophisticated equipment

• Faster detection of growth

• Higher sensitivity than solid media

• Can also be used for drug-

susceptibility testing

• Two examples:

• BACTEC

• MGIT

MGIT

BACTEC


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Culture: Identification of Mycobacteria

Growth characteristics (preliminary ID)

• Preliminary indication of M.tb can be determined from colony

characteristics

• Rate of growth

• Colonial morphology

• Pigmentation

Biochemical tests

• There is a battery of 8 – 12 biochemical tests used to

differentiate M.tb within the genus

• Nitrate reduction and niacin production are definitive for M.tb


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Smooth, buff-colored

colonies suggestive of

Mycobacterium avium

complex Rough, buff-colored colonies

suggestive of Mycobacterium

tuberculosis

Culture: Identification of Mycobacteria

Visual assessment of colony morphology:


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Culture: Cross-Contamination

• Be aware that faulty

technique can lead to

laboratory cross-

contamination of

specimens (difficult to

verify without access to

more technical testing).

• Adequate quality control is

an essential component of

any mycobacteriology

laboratory.


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Rapid Diagnostic Testing

Nucleic acid probe tests (non-amplified) to

identify organisms grown in culture:

• DNA probe tests are species or complex specific

• Commercial probes are available for M.tb complex, MAC, M.

kansasii and M. gordonae

Nucleic acid amplification tests (NAAT):

• These tests are designed to amplify and detect DNA

specific to M.tb

• Enables direct detection of M.tb in clinical specimens


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Other Rapid Diagnostic Tests

• Loop-mediated isothermal amplification (LAMP)

• Rapid, simplified NAAT still under investigation

• May be more feasible in lower resource settings

• Immunological tests

• Serologic tests for antibody, antigens, and

immune complexes; not currently accurate

enough to replace microscopy and culture.


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Other Rapid Diagnostic Tests

• High performance liquid chromatography (HPLC)

• HPLC uses a liquid chromatography method to identify mycobacteria based on their mycolic acid profiles (cell wall composition)

• The equipment is expensive and is usually reserved for larger, specialized, reference laboratories


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Rapid Drug Susceptibility Tests

• Line-probe assays

• Identifies M.tb and genetic

mutations associated with

INH and RIF resistance

• Can be used directly on

sputum specimens, results

within 1-2 days Molecular beacons

Bacteriophage-based assays

*GenoType MTDBRplus strips

(Hain Lifescience)

*Barnard et al. Am. J. Respir. Crit. Care Med 2008; 177: 787-792

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National Tuberculosis Control

Program (NTP)

• Objectives

• Reduce mortality, morbidity and disease transmission and avoid the development of drug resistance

• In the long term, to eliminate suffering due to TB


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Goals of the NTP

• Detect at least 70% of the infectious cases

• Cure at least 85% of newly detected cases of smear-positive TB

• Reduce prevalence of and deaths due to TB


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NTP • Case finding, which is the identification and

diagnosis of TB cases among individuals with

suspected signs and symptoms of TB, is a basic

step in TB control.

• Fundamental to case finding is the detection of

infectious cases through direct sputum smear

microscopy (DSSM).

• DSSM results serve as basis for categorizing TB

symptomatics according to standard case definition,

monitor progress of patients with sputum smear-positive

TB while they are receiving anti–TB treatment

• These are also used to confirm cure at the end of

treatment.

NTP MOP 2005

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NTP

National TB Reference Laboratory

• Quality assurance of sputum microscopy smear

are done quarterly

• Objectives of QA program: • ensure that the reported results are accurate

• identify practices that are potential sources of error

• ensure that appropriate corrective actions are initiated

NTP MOP 2005

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What is STOP TB Strategy

1. Pursuing quality DOTS expansion and enhancement

2. Addressing TB/HIV and MDR-TB

3. Contributing to health system strengthening

4. Engaging all care providers

5. Empowering patients and communities

6. Enabling and promoting research


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TB Pathogenesis Exposure

Infection

Active Disease

Inactive Disease

Who has Tuberculosis?

STOP TB AT THE SOURCE!

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DOTS Component of STOP TB

Strategy

• Political commitment to TB control

• Case detection by quality assured bacteriology

• Regular, uninterrupted supply of high quality anti-TB drugs

• Standardized treatment with supervision and patient support

• Standardized recording and reporting


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Benefits of DOTS

• Produces cure rates of up to 95 %

• Prevents new infections

• Prevents the development of MDR-TB

• Cost effective


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IMPORTANCE OF ACID-FAST BACILLI (AFB)

MICROSCOPY IN DOTS PROGRAMS

• Diagnosis

• Treatment Follow-up

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Role of Laboratory

• Detection of infectious cases

• Monitoring of treatment progress

• Documentation of cure


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Detection and treatment

of infectious cases

reduces the spread of

Tuberculosis!


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• AFB smear-positive patients are usually sick and seek treatment.

• AFB smear-positive patients are much more likely to die if untreated.

• Untreated, an AFB smear-positive patient may infect 10–15 persons/year.

Pulmonary Positive Patients


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NTP RESPONSE TO MDR-TB PROBLEM

• Policy and technical support:

AO 2008-0018: “Guidelines for the Implementation of

PMDT”

• Implementing guidelines and training modules for

PMDT

• Mainstreaming of MDR-TB services to the NTP

• Public-private collaboration from diagnosis to

management of cases

NTP MOP 2005

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ISTC Standard 12

• Patients with or highly likely to have tuberculosis caused by drug-resistant (especially MDR/XDR) organisms should be treated with specialized regimens containing 2nd-line antituberculosis drugs

• The regimen chosen may be standardized or based on suspected or confirmed drug susceptibility patterns

• At least four drugs to which the organisms are known or presumed to be susceptible, including an injectable agent, should be used, and treatment should be given for at least 18–24 months beyond culture conversion

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Intermediate

laboratories

Peripheral Laboratories

Laboratory Network

Central

Laboratory


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• Located within a general dispensary, clinic or hospital

• Limited services for TB diagnosis

• Sputum specimen collection

• AFB sputum smear microscopy

Peripheral Laboratory


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• Regional/provincial or large hospital

• Services for TB diagnosis

• Sputum specimen collection

• Sputum smear microscopy

• Culture and identification of MTB

• Support for peripheral laboratories

• Supply of reagents and materials

• Training, supervision, EQA of sputum smear microscopy

Intermediate Laboratory


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• Country/regional level

• Services for TB diagnosis

• Sputum smear microscopy

• Culture and identification of MTB

• Drug susceptibility testing of TB

• Support for the laboratory network

• Advice on procurement

• Organization and participation in training, supervision, EQA of sputum smear microscopy

• Other activities

• Participation in operational research

• Drug resistance surveillance

Central Laboratory


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Laboratory is the key

Component in TB Control

NO LABS

NO DIAGNOSIS

NO TREATMENT

NO DOTS

NO TB CONTROL

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• What is TB and how it is transmitted?

• What are the ISTP Standards for Diagnosis?

• What are the goals of NTP?

• Why is microscopy an effective diagnostic technique?

• What is DOTS?

• What is the role of the laboratory in TB control?

Summary

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References

1. PTSI,DOH,RITM,NTRL, Training Manual (Training course on Direct Sputum Microscopy

2. http://wwwn.cdc.gov/dls/ila/acidfasttraining/section1.aspx#training

3. International Standards for Tuberculosis Care, 2009

4. http://www.who.int/tb/strategy/en/

5. NTP MOP 2005

http://wwwn.cdc.gov/dls/ila/acidfasttraining/section1.aspx



http://www.who.int/tb/strategy/en/

http://www.who.int/tb/strategy/en/