Instructor’s 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 www.istcweb.org
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.
• Toman’s tuberculosis. Case detection, treatment and ndmonitoring, 2 Edition. Freiden TR ed., World
Health Organization, 2004. www.who.int/tb
• 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
• 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
• 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
• 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
• An accurate TB diagnosis may be further
complicated due to the higher rate of
extrapulmonary and disseminated disease in
• 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
• 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 clinician’s suspicion for TB.
• Significant risk factors for possible recent
[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
• 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 “Pott’s 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
• 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
[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 www.tbreider.org]
• 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