Transcript tuberculin skin test

Prevention of tuberculosis.
Targeted Tuberculin Skin Testing
Lecturer MD, Ph.D. Furdela
Victoria
Assistant Professor, Pediatrics
Department #2, Ternopil State
Medical University, Ukraine
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Tuberculosis
in Children and Adolescents
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Epidemiology
Public Health Aspects & TB Control
• Targeted Tuberculin Skin Testing
• Contact Investigations
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BCG Vaccine
Treatment of Latent TB Infection and TB
Disease
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Global Epidemiology of TB

Tuberculosis remains the leading infectious
disease in the world
• More than 40% of the world’s population (>2
billion people) are infected with M. tuberculosis
• In the 1990s:
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90 million new cases
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30 million deaths
• Among children <15 years of age:
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Approximately 13 million cases
5 million deaths
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Reported TB Cases
United States, 1982-2003
No. of Cases
28,000
24,000
20,000
16,000
12,000
1983
1987
1991
1995
1999
2003
Year
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Number of TB Cases in
U.S.-born vs. Foreign-born Persons
United States, 1993-2003
20000
15000
10000
5000
0
1993
1995
1997
U.S.-born
CDC
1999
2001
2003
Foreign-born
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Trends in TB Cases in Foreign-born
Persons, United States, 1986-2003
No. of Cases
Percentage
10 000
60
8 000
50
40
6 000
30
4 000
20
2 000
0
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86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
No. of Cases
CDC
0
Percentage of Total Cases
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Reported TB Cases by Age Group
United States, 2003
<15 yrs
(6%)
65+ yrs
(20%)
45 - 64 yrs
(29%)
15 - 24 yrs
(11%)
25 - 44 yrs
(34%)
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Summary of Epidemiology of TB
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Cases and case rates are on the decline
Foreign born persons account for more than 50% of
U.S. cases
• New Jersey: 70%
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TB in children:
• Highest risk for disease:
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<5 years of age
Foreign born children
• 60% of cases develop within 18 months of arrival in U.S.
• Most common countries of birth: Mexico, Philippines, Vietnam
 Varies depending on immigration patterns, i.e., recent increases
in case among children from Sub-Saharan Africa and Eastern
Europe
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Racial and ethnic minorities
Significance of
Tuberculosis in Children
A case of tuberculosis in a child is
considered a “sentinel healthcare
event” representing recent
transmission of TB within the
community
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Children <15 years with TB
by Site of Disease
Extrapulmonary
20%
Pulmonary &
Extrapulmonary
5%
Pulmonary
75%
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Children <15 years with TB:
Extrapulmonary Disease
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12
5
8
6
63
Miliary
Lymphatic
Pleura
Meningeal
Bone/Joint
Other
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TB Control In the United States
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Identification of new cases of TB
• Initiation of appropriate treatment
• Directly observed therapy
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Contact Investigations
• Identify persons at risk for infection

Targeted tuberculin testing
• Identifies persons at high risk for TB who
would benefit by treatment of LTBI
• Treatment of latent TB infection (LTBI)
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Mantoux Tuberculin Skin Test
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Specificity of the test varies depending on the
prevalence of LTBI and the frequency of crossreactions to the PPD antigen in a given population
In a population with relatively high frequency
cross-reactions the specificity of the PPD is <95%
• Decreases the positive predictive value of positive test
in a low risk population
• If the specificity is 90% in a low risk population with a
prevalence of LTBI of 1%:
Positive predictive value of TST: 8%
 92% of positives are false positives
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• As prevalence of LTBI increases the PPV increases
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Mantoux tuberculin skin test
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AAP Recommendations:
Targeted Tuberculin Skin Testing
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Risk of exposure to TB should be assessed
at routine healthcare evaluations
Only children with an increased risk of
acquiring TB infection or disease should
be considered for testing
Frequency of testing should be according
to the degree of risk of acquiring infection
“Screening” is an inefficient way to control
tuberculosis
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Targeted Tuberculin Testing
Risk-Assessment Questionnaire
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Was your child born outside the United States?
• Africa, Asia, Eastern Europe, Latin America
Has your child traveled outside the United States? >1
week
Has your child been exposed to anyone with TB
disease? TB or LTBI, nature of contact
Does your child have close contact with a person who
has a positive TB skin test?
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Targeted Tuberculin Testing
Risk-Assessment Questionnaire

Depending on local epidemiology and priorities other
possible questions include:
• Does your child spend time with anyone who has
been in jail or a shelter, uses illegal drugs or has
HIV?
• Has your child had raw milk or eaten unpasteurized
cheese?
• Is there a household member born outside the U.S.?
• Is there a household member who has traveled
outside the U.S.?
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AAP Recommendations:
Tuberculin Skin Testing
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Children for whom immediate TST is indicated:
• Contacts of persons with confirmed or suspected
infectious tuberculosis (contact investigation)
• Children with CXR or clinical findings suggesting TB
• Children immigrating from endemic countries (e.g.,
Asia, Middle East, Africa, Latin America)
• Children with histories of travel to endemic countries
and/or significant contact with indigenous persons
from such countries
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AAP Recommendations:
Tuberculin Skin Testing
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Children who should have an annual
TST:
•Children with HIV infection
•Incarcerated adolescents
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AAP Recommendations:
Tuberculin Skin Testing

Some experts recommend that these children should
be tested every 2-3 years:
• Children exposed to the following persons:
 HIV-infected
 Homeless
 Residents of nursing homes
 Institutionalized or incarcerated adolescents or
adults
 Users of illicit drugs
 Migrant farm workers
• Foster children with exposure to adults in the
preceding high risk groups
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AAP Recommendations:
Tuberculin Skin Testing
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Children who should be considered for TST at 4-6 and 11-16
years of age:
• Children whose parents immigrated (with unknown TST
status) from regions of the world with high prevalence of
tuberculosis
• Children with continued potential exposure by travel to
endemic areas and/or household contact with persons
from endemic areas (with unknown TST status)
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Administering the Tuberculin Skin Test

Inject intradermally 0.1 ml of 5
TU PPD tuberculin
Produce wheal 6mm to 10mm in
diameter
 Placed and read by

experienced health
professionals
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Reading the Tuberculin Skin Test
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Read reaction 48-72 hours after injection
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Measure only induration
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Record reaction in millimeters
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Positive TST in Children:
Definitions
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Takes into account the following:
• Risk of infection (exposure)
• Risk of progression to disease
 Immune status
 Age
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Positive TST Results:
Infants, Children, and Adolescents
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TST considered positive at >5 mm induration when:
• In close contact with known or suspected contagious
cases of tuberculosis
• Suspected to have tuberculosis disease:
 CXR consistent with active or previously active
tuberculosis
 Clinical evidence of tuberculosis
• Receiving immunosuppressive therapy
• With immunosuppressive conditions
• With HIV infection
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Positive TST Results:
Infants, Children, and Adolescents
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TST considered positive at >10 mm induration in children:
• At increased risk of disseminated disease:
 Young age: <4 years of age
 Other medical conditions: Hodgkin disease, lymphoma,
diabetes mellitus, chronic renal failure, malnutrition
• With increased exposure to tuberculosis disease
 Born or whose parents were born in high-prevalence
regions of the world
 Frequently exposed to adults who are HIV-infected,
homeless, users of illicit drugs, residents of nursing
homes, incarcerated or institutionalized persons,
migrant farm workers
 Travel and exposure to high-prevalence regions of the
world
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Positive TST Results:
Infants, Children, and Adolescents
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TST considered positive at >15 mm
induration:
• In children >4 years of age without any
risk factors
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Evaluation of the Child
with a Positive TST
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Evaluation of all children with a
positive TST should include:
•A careful history
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Household investigation
•Physical examination
•Chest radiographs (PA & lateral)
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Treatment of
Latent Tuberculosis Infection in Children
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INH 10 mg/kg (max., 300 mg) PO daily for 270 doses
Alternative: Twice weekly directly observed (DOT) INH 20-40
mg/kg (max., 900 mg) PO for 72 doses
Monitor index case isolate sensitivities
Hepatotoxicity from INH is rare in children:
• A monthly assessment for clinical evidence of
hepatotoxicity should be made: loss of appetite or weight,
nausea, vomiting, abdominal pain, jaundice
• Routine monitoring of LFTs is not indicated
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Tuberculosis Control in the
United States
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Contact Investigations
“The most reliable TB control program is based upon
aggressive and expedient contact investigations,
rather than routine screening of large populations
with low risk.”
Can be complex, require experience and often a lot
of detective work.
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Tuberculosis Exposure in Children
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History, PE, TST, CXR done
• CXR is done regardless of TST result
IF:
• Asymptomatic and physical examination is normal
• TST is negative
• Chest X-ray is normal
AND IF <4 years of age START: Isoniazid (INH) 10
mg/kg (max., 300 mg) PO once daily
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Tuberculosis Exposure in Children
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Why is INH given even if there is no evidence of
infection or disease at initial visit:
• May already be infected
• Infection more likely to progress to disease
• Infants and younger children are more likely to have
disseminated disease or meningitis
TST repeated 12 weeks after contact broken with
infectious adult:
• If TST (-), discontinue INH
• If TST (+), re-evaluate child and treat accordingly
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Prevention of Tuberculosis in Children:
Missed Opportunities
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Failure to find and appropriately manage adult source
cases (Case finding)
Delay in reporting the initial diagnosis of TB
Contact investigation interview failure
Delay in evaluation of exposed children
Failure to completely evaluate exposed children
Failure to prescribe prophylactic INH
Failure to maintain a contact under surveillance
LTBI diagnosed; treatment not prescribed
Failure to complete treatment for LTBI (Adherence)
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BCG Vaccine
and Tuberculin Skin Testing
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History of a BCG is never a contraindication to tuberculin
skin testing
No reliable method of distinguishing (+) TSTs due to BCG
from those caused by infection with M. tuberculosis
Therefore, management of children with a history of BCG
and a (+) PPD includes:
• Diagnostic evaluation including a chest radiograph
• Appropriate treatment
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BCG – Fantasy and Fact
FANTASY
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
BCG protects against getting TB
infection
BCG provides lifetime protection against
developing active TB
FACT
•BCG will not protect against becoming infected
with TB
•BCG protects against severe complications of
TB disease in young children,
but provides little or no protection in adolescents
and adults

BCG causes the tuberculin skin test (TST)
to be positive for life
•BCG causes the TST to be positive for
a few years and then the TST reaction becomes
much weaker. Generally, no reaction is present
after 5 years.
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In a BCG-vaccinated person, a positive
TST is most likely due to BCG
A positive TST in a person of any age
from any country is most likely due to
BCG, not TB infection
There is no need for a BCG-vaccinated
person with a positive TST to be treated
•There is no way to tell whether a positive TST is
due to BCG or to TB infection
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•A positive TST in an adolescent or adult from a
TB high-burden country is almost always due to
TB infection, not BCG
•Persons with a positive TST from
TB high-burden countries are at
high risk of developing active TB
and should be treated
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