By Keith Bell,2014-04-26 07:12
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Instructors Guide and Teaching Notes

    Module: Clinical Presentation and Diagnosis of Tuberculosis Slide 1 ISTC Standards covered: 1 5

    Module Time: Approximately 60 minutes

    Alternate slides: Introductory ISTC slides.

    Interactive options: Ideas for interactive discussions are offered on many of the slides in this module. Participant discussion can enhance active learning, but will add more time to the lecture and must be planned for.

    Slide-show Animation: A second version of this talk is

    available with slide animations: Clinical Presentation and Diagnosis of TB (Animated).

    Additional Material: Slides containing related material may be found in the following modules: Microbiological diagnosis of Tuberculosis, TB and HIV Infection: Introduction and Diagnosis.

    Test Questions: May be attached or inserted within

    presentation for discussion purposes, or alternatively, combined with questions from other modules to produce evaluation tool.

    The full text of the ISTC and all supporting references are available at

    Other useful Resources/References:

     Management of tuberculosis training for health

    facility staff. World Health Organization, 2003.

     Radiographic Manifestations of Tuberculosis: A

    Primer for Clinicians, Second Edition. Francis J.

    Curry National Tuberculosis Center.

     Tomans tuberculosis. Case detection, treatment and ndmonitoring, 2 Edition. Freiden TR ed., World

    Health Organization, 2004.

     A Tuberculosis Guide for Specialist Physicians. Jose

    A. Caminero Luna, IUATLD, Sept. 2004.

     [Image credit: World Lung Foundation/Jad Davenport]

    Clinical_diagnosis_Nov2009.ppt Page 1 of 24

     It is intended that after completion of this

    module the student will be able to describe

    Slide 2 the approach to diagnosis of TB and the

    proper role of diagnostic testing, particularly

    sputum microscopy, in that process.

     [Review objectives from slide]

     Overview of Clinical Presentation and

    Diagnosis of TB

    Slide 3 [Review content of slide]

     Lecture/module includes International

    Standards 1 - 5

     [Image of sputum smear photomicrograph

    reveals Mycobacterium tuberculosis bacteria

    using acid-fast Ziehl-Neelsen stain]

    [Image credits: World Lung Foundation/Jad Davenport (top);

    CDC Public Health Image Library/Dr. George P. Kubica (bottom)]

     In introducing the Standards for Diagnosis

    of TB, it is important to recognize: [Review

    Slide 4 content of slide]

    [Image credit: World Lung Foundation/Virginia Arnold]

Clinical_diagnosis_Nov2009.ppt Page 2 of 24

     Therefore, two fundamental points that

    should be stressed are: [Review content of

    Slide 5 slide]

     To diagnose TB, we must Think TB.

    [Image credit: World Lung Foundation/Pierre Virot]

    Begin with: Classic TB clinical presentation

    Slide 6 The most common symptom of pulmonary

    TB is persistent productive cough, often

    accompanied by nonspecific constitutional

    symptoms, such as fever, night sweats, and

    weight loss.

     Extra-pulmonary TB, such as

    lymphadenopathy, may be noted, especially

    in patients with HIV infection.

     Nonspecific systemic, constitutional

    symptoms may include:

    Slide 7 [Review content of slide]

     It is important to also recognize that there

    are many cases of TB, up to 10-20%, that

    may present without any symptoms at all.

Clinical_diagnosis_Nov2009.ppt Page 3 of 24

The diagnosis of TB with HIV co-infection can be

    more difficult.

    Slide 8

     Symptoms may be more nonspecific, but

    fever and weight loss may be more

    prominent at presentation.

     Cough and hemoptysis are less common

    because there may be less cavitation,

    inflammation and endobronchial irritation in

    HIV patients.

     CXR findings can be more variable, with

    both typical, post-primary or reactivation

    TB and “atypical, primary TB” CXR

    patterns commonly seen. In people

    infected with HIV, obtaining a timely CXR

    plays an important role in shortening delays

    in diagnosis and should be performed early

    in the investigation of a TB suspect.

     The diagnosis of TB may be further

    complicated by the broader range of possible

    alternative diagnoses. The physical signs of

    respiratory infection in patients with

    pulmonary TB (PTB) do not readily

    distinguish PTB from other chest diseases

    and chest examination may even be normal.

    Because of the broader differential

    diagnosis, access to and utilization of culture

    and more invasive diagnostic become more

    important issues.

     An accurate TB diagnosis may be further

    complicated due to the higher rate of

    extrapulmonary and disseminated disease in

    HIV-infected individuals.

     So what guidance do the International

    Standards for TB Care offer for prioritizing

    Slide 9 who to evaluate for the diagnosis of TB?

     Standard 1: [Read Standard]

[Image credit: WHO]

    Clinical_diagnosis_Nov2009.ppt Page 4 of 24

     Although most patients with pulmonary TB

    have cough, the symptom is not specific to

    TB; it can occur in a wide range of Slide 10 respiratory conditions, including acute respiratory tract infections, asthma, and

    chronic obstructive pulmonary disease.

     While the presence of cough for 2-3 weeks

    is nonspecific, traditionally, having cough of

    this duration has served as the criterion for

    defining suspected TB and is used in most

     national and international guidelines,

    particularly in areas of moderate- to high-

    prevalence of TB.

     Data from India, Algeria, and Chile

    generally show that the percentage of

    patients with positive sputum smears

    increases with increasing duration of cough,

    and a more recent assessment from India

    demonstrated that by using a threshold of >2

    weeks to prompt collection of sputum

    specimens, the number of TB cases

    identified increased by 46%. Simply

    inquiring about cough can increase yield of

    cases identified.

     Certainly, duration of cough is not the only

    criterion that should raise suspicion for

    tuberculosis, other features of the

    presentation may raise your concern for TB

    in patients with a shorter duration or even

    absence of cough, therefore clinical intuition

    plays an important role in the evaluation for

    TB. This is particularly true with HIV co-

    infection where TB presentation may be

    more atypical and lack of cough more


     [Reference: Santha T., et al. Comparison of cough 2

    and 3 weeks to improve detection of smear-positive

    tuberculosis cases among out-patients in India. Int J

    Lung Dis 2005;9(1):61-8]

    Clinical_diagnosis_Nov2009.ppt Page 5 of 24

    In evaluating persons who have symptoms that my be caused by TB it is important to identify risk factors for either: Slide 11 Recent infection with M.tb due to

    transmission risks and/or factors that may

    increase the likelihood of progression to

    active TB once an individual is infected.

     The presence of any of these factors should

     raise the clinicians suspicion for TB.

     Significant risk factors for possible recent

    infection include:

     [Review content of slide]

     Significant risk factors that may increase the

    likelihood of progression to active TB once

    an individual is infected include: Slide 12 [Review content of slide]

     [Interactive option ask participants what

    risk factors are most prevalent in their local

    areas and practices? Are there any other

    special groups or settings not listed here that

    are important to their region?]

     The physical examination is non-specific in

    TB but useful to identify sites of TB:

     [Review content of slide] Slide 13

    Clinical_diagnosis_Nov2009.ppt Page 6 of 24

     In persons who are suspected of having TB

    based on symptoms and/or physical findings,

    every effort must be made to identify the Slide 14 causative agent. The first important step is highlighted by the

    International Standard 2: [Read Standard]

     [Note: Guidelines have recently changed

    from three sputum smears to at least two

    sputum smears. The change is reflected

    above and differs from the wording in the

     original published ISTC]

     [Image shows sputum smear with

    carbolfuchsin-based stain demonstrating

    typical acid-fast bacilli morphology]

    [Image credit: CDC Public Health Image Library /Dr. George P. Kubica]

     While a definitive microbiological diagnosis

    can only be confirmed by culturing M.

    tuberculosis complex (or, under appropriate Slide 15 circumstances, identifying specific nucleic acid sequences) from clinical specimens, in

    practice, there are many settings where these

    tests are not currently feasible (due to

    resource limitations).

     Fortunately, microscopic examination of

    stained sputum, i.e. an AFB smear, is

     feasible in nearly all settings.

     In almost all clinical circumstances in high

    prevalence areas, finding acid-fast bacilli in

    stained sputum is highly specific and, thus,

    is the equivalent of a confirmed diagnosis.

     In addition to being highly specific for M.tb,

    identification of AFB by smear is

    particularly important for three reasons:

     It is the most rapid method for

    determining if a person has TB

     It identifies persons who are at

    greatest risk of dying from the


     And it identifies the most likely

    transmitters of infection

    *[Note that in persons with HIV infection, mortality rates are greater in patients with clinically-diagnosed TB who have

    negative sputum smears than among HIV-infected patients

    who have positive sputum smears.]

    Clinical_diagnosis_Nov2009.ppt Page 7 of 24

     The limitation of sputum smear microscopy

    is its sensitivity.

     As illustrated in the table: compared with Slide 16 culture, sputum smear microscopy is 68% sensitive in detecting M. tuberculosis.

     Of all specimens that are AFB positive

    nearly 86% are detected by examining one

    specimen and an additional 12% are found

    on the 2nd specimen; thus, the incremental

    rd specimen is very low. A yield of the 3

     similar increment is found for the sensitivity

    ndrdof the 2 and 3 specimens.

     The yield is better with a single early

    morning specimen than with a spot specimen

    obtained at other times during the day.

[Reference: Mase SR, et al. Yield of serial sputum specimen

    examinations in the diagnosis of pulmonary tuberculosis: a

    systematic review. Int J tuberc Lung Dis 2007;11(5): 485-95]

    While we often focus on the pulmonary presentation and evaluation for TB, it is important to remember that TB may present in many ways. Slide 17

     Can this case be TB?

     A 54 year-old man with three months of

    focal low back pain presents with this radiographic finding.

[Interactive option ask participants to respond to

    question of TB for this case.]

    [Image credit: Francis J. Curry National Tuberculosis Center, University of California, San Francisco]

    Clinical_diagnosis_Nov2009.ppt Page 8 of 24

    Yes, this is a patient presenting with spinal TB, or Potts disease, with radiographic evidence of

    vertebral destruction. Slide 18 Site specific symptoms are often the catalyst

    for discovery of extrapulmonary sites of


     While the radiographic findings in this case

    may easily bring TB into the differential

    diagnosis for this patient, often with

     extrapulmonary disease, pertinent TB risk

    factors must be recognized by the astute

    clinician for TB to be considered and proper

    diagnostic testing (which include both

    culture and histopathologic sampling if

    available) be initiated.

[Interactive option Ask participants for their

    experiences with cases of extrapulmonary TB where the diagnosis was a surprise. What kind of

    sampling/testing for extrapulmonary disease is available to them in their practice? Any creative solutions to difficulties encountered in obtaining diagnostic samples or possibilities for shared resources?]

[Image credit: Francis J. Curry National Tuberculosis Center,

    University of California, San Francisco]

    Clinical_diagnosis_Nov2009.ppt Page 9 of 24

    Standard 3 reinforces these points: [Read Standard 3]

     Slide 19 Clearly, appropriate specimens may be difficult to obtain from some

    extrapulmonary sites.

     In spite of the difficulties, however, the basic

    principle that bacteriological confirmation of

    the diagnosis should be sought still holds.

     Generally, there are fewer M. tb organisms

     present in extrapulmonary sites, so

    identification of acid-fast bacilli by

    microscopy in specimens from these sites is

    less frequent and culture is more important.

     If tissue biopsy material is obtained,

    diagnosis of TB may also be suggested by

    histopathologic demonstration of appropriate

    granulomatous lesions.

[Instructor Notes: If the Microscopic Diagnosis

    module will not be covered in your curriculum, consider reviewing the Microscopic Diagnosis module for additional speaking points or slides that would be of interest for this topic.]

[Image credit: IUATLD]

     Extrapulmonary TB (without lung

    involvement) accounts for 15-20% of TB in

    populations with a low prevalence of HIV Slide 20 infection. In populations with a high prevalence of

    HIV infection, the proportion of cases with

    extrapulmonary TB is higher.

     Here, as a general example, is the

    breakdown of extrapulmonary involvement

    by site as reported in the United States.

     [Review content of slide]

    Clinical_diagnosis_Nov2009.ppt Page 10 of 24

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