Tuberculosis
Mark B. Stephens, MD MS FAAFP
CDR MC USN
Assoc Prof Fam Med USU
Cap Conf 2008
6 Key Learning Points
1. Assess for TB Risk
2. If risk present, perform TST/IGF test
3. If TST +, r/o active TB
4. If no active TB, treat LTBI
5. Ensure completion of LTBI
6. If active TB, isolate and treat
*IGT = interferon gamma testing
Which one of the following is true
regarding PPD testing for tuberculosis?
1. Patients who have converted within the past
year should be treated, regardless of age
2. In patients who previously received a BCG
vaccination, the threshold for a positive test
is 25 mm of induration
3. Patients who test positive only on the second
step of a two-step PPD test, given 2 weeks
after the first test, are at high risk for
development of active disease
4. PPD testing is contraindicated in patients
who are HIV positive
1
A health-care worker has a negative
tuberculin skin test. A second test 10 days
later is positive.
This result indicates
1. previous vaccination with BCG
2. a false-positive skin test
3. recent conversion
4. long-standing, latent infection
5. probable immunodeficiency
4
Which persons are at increased
risk of contracting active TB once
infected with m. tuberculosis?
1. Persons with HIV infection
2. Persons who live in dry climates
3. Persons who inject illicit drugs
4. Persons with a history of inadequately
treated TB
1, 3, 4
1/3 of the World Population is
infected with tuberculosis
1. True
2. False
How many worldwide deaths
annually from TB?
1. 2 million
2. 500,000
3. 6 million
4. 10 million
5. 20 million
How many people develop active
TB annually?
1. 6 million
2. 9 million
3. 12 million
4. 15 million
5. 18 million
Objectives
1. Assess for TB risk
2. Determine criteria for screening tests
and interpretation
3. Analyze factors associated with active
TB
Primary resource
Which one of these increases a
person’s risk of exposure to TB?
1. Adolescents participating in outdoor
sports
2. Family members living with someone
who has TB
3. Employees of a correctional facility
4. Foreign-born persons from areas that
have a high TB prevalence
2, 3, 4
Who is at risk?
1. Close contacts of persons known or
suspected to have TB
2. Foreign-born persons, including children,
from areas that have a high TB prevalence
3. Residents and employees of high-risk
congregate settings
4. Some medically underserved, low-income
populations as defined locally
1, 2, 3, 4
Who is at risk?
1. High-risk racial or ethnic minority
populations, defined locally as having an
increased prevalence of TB
2. Infants, children, and adolescents exposed
to adults in high-risk categories
3. Persons who inject illicit drugs
4. Health care workers who serve high-risk
clients
1, 2, 3, 4
Who needs TST?
1. 20 yo school teacher
2. 54 yo diabetic
3. 43 yo Indonesian immigrant
4. 55 yo inmate
5. ALL of the above
3, 4*
Targeted Tuberculin Skin Test
• Best screening tool available
• Useful for
– Determining how many people in a group
are infected (e.g., contact investigation)
– Examining persons who have symptoms of
TB
• Multiple puncture tests (e.g., Tine Test)
are inaccurate and not recommended
QuantiFERON®-Gold Test
• Whole-blood test used to detect M.
tuberculosis infection
• Cells recognize tubercle protein-
specific antigens and release
interferon-γ (IGT)
LTBI
• LTBI preferred to “PPD Converter”
• LTBI is the presence of M. tuberculosis
organisms without symptoms or
radiographic evidence of TB disease
LTBI
• Finding and treating persons at high risk
for latent TB infection (LTBI) is a priority
• Without treatment 10-15% LTBI
proceed to active TB
A 26-year-old female nurse has had recent contact with
patients with AIDS and tuberculosis (TB), and now has
a positive tuberculin skin test. Her test was negative a
year ago. She has no other medical complaints. Testing
to exclude which one of the following is most important
before starting latent TB therapy with isoniazid (INH)?
1. Active TB
2. Previous hepatitis
3. Diabetes mellitus
4. Neuropathy
5. Pregnancy
1
Who is at risk to develop active
TB?
1. Those who have been recently
infected
2. Those with clinical conditions that
increase their risk of progressing
from LTBI to TB disease
1. Recent Infections
• Close contacts to person with infectious
TB
• Skin test converters (within past 2
years)
• Recent immigrants from TB-endemic
regions of the world (within 5 years of
arrival to the U.S.)
2. Clinical Conditions
• Children ≤ 5 years with a positive TST
• Residents and employees of high-risk
congregate settings (e.g., correctional
facilities, homeless shelters, health care
facilities)
• Underweight or malnourished persons
• Injection drug users
RR for Active TB
Clinical Condition Relative Risk
Silicosis 30
DM 2.0-4.1
ESRD 10.0-25.3
RRT / Dialysis 37
Solid organ Transplant 20-74
Carcinoma H&N 16
HIV+ 35-162
Recent LTBI ( 15 years
ago
• Works in a correctional facility
• TST result negative 1 year ago
• TST employment physical = 26 mm
• CXR normal
• No symptoms of TB disease
• No known contact with a TB patient
What are this patients risk factors
for TB?
1. Female
2. Philippines
3. Correctional work
4. Recent TST conversion
Case Study 3
• Recent TST conversion (within a 2-
year period)
• TST conversion increases risk for
progressing from LTBI to TB disease
• Foreign-born status is less of a risk
factor (immigrated > 5 years ago)
• Correctional work
Case Study 3
• Patient is a recent ‘converter’ and, as
such, is a candidate for treatment of
LTBI with INH
BOARD QUESTIONS
A 36-year-old male who recently immigrated
from Rwanda presents with a several-month
history of cough accompanied by hemoptysis
and weight loss. He is afebrile, and a lung
examination is normal. A chest radiograph
shows a cavitary lesion in his left upper lobe. He
is admitted to the hospital and placed in
respiratory isolation. A tuberculin test is
positive, but three induced sputum smears are
negative for acid-fast bacillus. Cultures are still
pending. Which one of the following INITIAL
treatment regimens is most appropriate?
1. No treatment until culture results are
available
2. Isoniazid for 9 months
3. Rifampin and pyrazinamide for 8 weeks
4. Rifampin and/or isoniazid for 18 weeks
5. Rifampin, isoniazid, ethambutol, and
pyrazinamide for 8 weeks
5
•High incidence in sub-Saharan Africa.
•Positive AFB smear/culture for M. tb to
confirm active disease,
•Treatment should begin without delay if
suspicion is high (four drugs)
•Initial treatment for previously untreated is
8 weeks of rifampin, isoniazid, ethambutol,
and pyrazinamide.
•If the likelihood of active tuberculosis is low,
treatment can be deferred until the results of
mycobacterial cultures are known.
Resources
• http://www.cdc.gov/tb/webcourses/Core
Curr/index.htm
• http://ntcc.ucsd.edu/