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Module 15 – March 2010
TB Contact
Investigation
Project Partners
Funded by the Health Resources and Services Administration (HRSA)
Module Overview
Overview:
 Value (yield) of contact
evaluation
 Clinical factors
influencing transmission
 Evaluating contacts and
determining priorities
 Vulnerable contacts
 Treatment of infected
contacts
International Standards 18 and 19
Learning Objectives
At the end of this presentation participants
will be able to:
 Describe the criteria used and method for
determining an infectious period
 Evaluate the risk of transmission based on
the clinical extent of disease and diagnostic
tests
 Determine who among contacts is at greatest
risk should infection occur
 Identify and evaluate contacts who are at
increased risk for TB infection
Definitions
 Case – a particular instance of disease
(e.g., TB). A case is detected,
documented and reported
 Index case – the first person who
presents for evaluation as a confirmed or
suspected case of tuberculosis
 Source case – the case or person that
was the original source of infection for
secondary cases or contacts
Definitions (2)
 Contact –someone who is at risk for
acquiring M. tuberculosis infection by
sharing airspace with an index case
 Converter – a person whose test result
for M. tuberculosis has changed from
negative (uninfected) to positive (infected)
 Window period – refers to the interval
between infection and detectable
reactivity to the tuberculin skin test (TST)
Why do we do TB contact
investigations (CI)?
Remember!! Every TB Case
Began as a TB Contact
Contact investigation
helps to:
TB Index Case
 Identify additional
TB cases
 Identify persons
with latent TB
infection
TB Case
TB Contacts
 Prevent the further
spread of TB
 Save someone’s life
TB Contacts
TB
Cases
ISTC Standard 18
All providers of care for patients with TB should
ensure that persons who are in close contact with
patients who have infectious TB are evaluated and
managed in line with international
recommendations. The determination of priorities
for CI is based on the likelihood that a contact:
1. Has undiagnosed TB
2. Is at high risk of developing TB if infected
3. Is at risk of having severe TB if the disease
develops
4. Is at high risk of having been infected by the index
case
ISTC Standard 18 (2)
The highest priority contacts for evaluation are:
 Persons with TB
symptoms
 Children aged <5 years
 Contacts with known
or suspected
compromised immune
systems, particularly HIV infection
 Contacts of patients with MDR/XDR tuberculosis
 Other close contacts are a lower priority group
Standards for Public Health
Systematic Review of Contact Investigations
 Yield for all active TB among household
contacts was 4.5%
 Pooled yield for confirmed TB among
household contacts was 2.3%
 Nearly one-half of the household contacts
evaluated had LTBI indicated by a
positive tuberculin skin test, but a
negative evaluation for active TB
Morrison J, et al. Lancet ID 2007
Yield: Active TB and LTBI by Age
TB1
LTBI2
Children
< 5 years
12
30.4
5 –14
17
47.9
15
64.6
Adults
1
Number needed to evaluate to find 1 case of TB
2 % of examined contacts with latent TB infection
Morrison J, et al. Lancet ID 2008;8(6)
TB Contact Investigation Steps
1. Decide whether to initiate a contact
investigation
2. Interview the index case
5
7
6
3. Examine sites of transmission
4. Prioritize contacts
4
3
5. Locate and evaluate contacts
6. Treat and follow-up contacts
1 2
7. Evaluate contact investigation activities
Step 1: Decide if a CI should be initiated
To make this decision, you will be
assessing for:
 Evidence that the index case may be
infectious
 Presence of vulnerable contacts
• Those with an immature or weakened
immune system
Review Medical Record
 Site of TB disease
 TB symptoms and approximate date of onset
 Test results
• Sputum AFB smear and culture results
 Including dates of specimen collection
• Chest X-ray results and date
 TB treatment (medications, dosage, and date
treatment was started)
 Method of treatment administration
• DOT or self-administered
Assessing Infectiousness
 High degree of infectiousness
• Sputum smear-positive pulmonary TB (PTB)
• Symptomatic with cough
• Cavitation on chest radiograph (correlates with
positive smear)
• Laryngeal tuberculosis
 Lesser degree of infectiousness
•
•
•
•
Sputum smear-negative, culture-positive PTB
Minimal if any cough
Lesser radiographic extent of disease
Extrapulmonary TB
Indices of Infectiousness
Tuberculin Reactors (%)
among household contacts
Radiographic extent of disease
Minimal
16.1
Moderately advanced
28.3
Far advanced
61.5
Bacteriologic status
Smear –, culture –
14.3
Smear –, culture +
21.4
Smear +, culture +
44.3
Mean 8-hour overnight cough count
< 12
27.5
12-48
31.8
48
43.9
Source-Case Variables
Loudon RG. ARRD 1969;99:109
Prevalence of Infection in Contacts
Source case status
Age
(yrs)
Smear + Smear – Smear –
General
Culture ? Culture + Culture – Population
0-4
29.1%
6.0%
6.5%
0.7%
5-9
35.9
12.4
6.2
0.9
10-14
39.5
14.1
19.1
2.2
15-19
47.0
18.1
18.1
4.2
20-29
51.5
32.9
43.4
10.5
30-39
59.2
52.2
46.2
21.3
40+
61.1
50.3
47.9
38.5
Grzybowski S. BIUAT 1975;60:90
How do we decide to initiate
the contact tracing process?
Decision to Initiate TB Contact Tracing
Site of disease
Pulmonary/
laryngeal/
pleural/ miliary
AFB * sputum
smear positive
Pulmonary suspect
(tests pending, e.g.,
sputum, cultures)
AFB sputum smear-negative
Abnormal CXR**
indicates cavitary
disease or TB
culture positive
Contact
tracing
should
always be
initiated
*
Acid-fast bacilli;
Non-pulmonary and/or extra
pulmonary (pulmonary and
laryngeal involvement ruled out)
Contact
tracing
should
always be
initiated
Abnormal CXR **
non-cavitary
consistent with
TB
Contact
tracing should
be initiated if
sufficient
resources
* * Chest radiograph
Abnormal
CXR NOT
consistent
with TB
Contact tracing
should be
initiated only
in extreme
circumstances
Contact
tracing
NOT
indicated
Who is Responsible for Conducting TB
Contact Investigations?
The National TB Program is responsible
for ensuring contact tracing occurs and
this includes ensuring:
 Identification and evaluation of contacts
 Treatment of contacts found to have TB disease
 Preventive treatment of contacts with TB
infection
 Monitoring of treatment and adherence to
prescribed regimens
 A system is in place to assess completion of
treatment
How Quickly Should a TB Contact
Investigation be Carried Out?
 Begin as soon as TB is diagnosed or
strongly suspected in a patient
 Initiate no more that 7 working days after
the case is reported to the National TB
Program
 Contacts should be examined within 14
working days after the index patient has
been diagnosed
Rationale for Prompt Contact Tracing
 Some contacts may develop TB disease
very quickly after being exposed to and
infected with M. tuberculosis
• Infants and children <5 years of age
• HIV-infected or other immunosuppressed
 Increases likelihood that all contacts will
be found and evaluated
Contact Investigation Case Study
Part 1
Step 2: Interview the Index Case
 Conduct a minimum of 2 interviews
• 1st interview
 ≤1 business day of reporting
for infectious patients
 ≤3 business days for others
• 2nd interview
 1–2 weeks later
• May need additional
interviews
TB Interview Goals
 Provide appropriate TB education
 Identify problems/concerns
 Determine period of infectiousness (IP)
and where patient spent time during IP
 Identify contacts and locating information
 Establish contact investigation priorities
 Reinforce follow through with treatment
plan
Circles of Contacts
Index case
Uninfected, 2
Uninfected, 10
Infected, 3
Infected, 5
Household Contacts
Average 4 – 5/case
Out-of-Household
Contacts
(Work, school, social)
Unknown number
Morrison J, et al. Lancet ID 2008;8(6)
Initial Interview Preparation
1. Review TB patient’s
medical records
2. Determine interview
objective and strategy
3. Arrange interview
place and time
TB Interview Components
 Introduction
 Education
 Contact List
 Conclusion
 Follow-up
Identification of Contacts
 Focus on those in the same household but
don’t neglect out-of-household contacts
 Tailor interview to patient’s circumstances
(homeless, congregate living facility, etc.)
 Determine the circumstances of exposure,
and attempt to quantify the closeness and
duration
 Determine if there are other persons within
the group of contacts who have symptoms
associated with TB
Determine Infectious Period
 The timeframe during which an individual
with TB disease is capable of transmitting
infection
 This timeframe is determined by
estimating the duration of the individual’s
symptoms, especially coughing
 In the absence of symptoms, this
timeframe is determined based on the
date of diagnosis of TB disease
Estimating Onset of Infectious Period
Characteristic
TB
AFB sputum
symptoms? smear positive?
Cavitary chest Recommended minimum beginning
radiograph?
of likely period of infectiousness
Yes
No
No
3 months before symptom onset or
1st positive findings consistent with
TB disease, whichever is longer
Yes
Yes
Yes or No
3 months before symptom onset or
1st positive findings consistent with
TB disease, whichever is longer
No
Yes
Yes or No
3 months before 1st positive finding
consistent with TB disease
No
No
Abnormal,
not cavitary
4 weeks before date of diagnosis
as a TB suspect or confirmed case
SOURCE: Modified from the California Department of Health Services Tuberculosis Control Branch; California Tuberculosis
Controllers Association. Contact Investigation Guidelines. Berkley, CA: California Department of Health Services; 1998, p.23.
Closing the Infectious Period
Infectious period closed when all the
following criteria are met:
 Effective treatment for ≥ 2 weeks,
 Diminished symptoms, and
 Bacteriologic response
Contact Investigation Case Study
Part 2
Step 3: Examine Sites of Transmission
 Visit the sites where the patient spent
time during the infectious period
 Components of the field investigation
include:
• Interview, test & provide TB
information to contacts
• Identify additional contacts
• Assess physical conditions of the
setting (room size, ventilation,
airflow, etc.)
Levels of Exposure
Closeness and duration of exposure:
 Grading exposure settings
1.
2.
3.
4.
Size of a car
Size of a bedroom
Size of a house
Larger than a house
Estimating critical exposure duration
 Thresholds are highly variable
 Exposure duration threshold should be
determined by index case characteristics,
settings, contact risk factors
Step 4: Prioritize Contacts
Concentric Circle Approach
Concentric Circle
Approach
Household / Residence
Environment
+
 Infectiousness
Index
Patient
Leisure / Recreation
Environment
Work / School
Environment
 Exposure
intensity
 Susceptibility
of the contact
Close contacts (high risk)
Other-than-close contacts (medium risk)
Other-than-close contacts (low risk)
Prioritizing Contacts
 High priority contacts
are determined by:
1. Most likely to be
infected
2. Most likely to progress
to disease if infected
Factors for Assigning Priority
Consider:
 Infectiousness of the
TB case
 Environment where
transmission likely
occurred
Infectiousness
Environment
Freq/duration
 Frequency, duration and proximity of
exposure
 Susceptibility factors:
• Age, immune system status
Priorities in Contact Evaluation
At greatest risk of acquiring infection
• Close contacts of smear positive index cases
• Persons with HIV infection
• Highly exposed persons
At greatest risk of active TB
• Children <5 years of age
• Persons with HIV infection
• Persons with other immunocompromising
conditions or therapies
Contact Investigation Case Study
Part 3
Step 5:
Locate and
Evaluate
Contacts
Initial Assessments of Contacts
 Approach to evaluation of contacts may vary
depending on local circumstances, resources,
and policies
 Evaluation: Question contacts about symptoms
and evaluate if symptoms are present
• TST followed by chest X-ray (CXR) for all positive
Mantoux (≥5 mm induration)
• CXR all children < age 5 and any symptomatic or
immunocompromised contacts regardless of TST
• Sputum examinations for all symptomatic
contacts and any with CXR abnormalities
suggestive of TB
Step 6: Treat & Follow-up Contacts
Rationale:
 Risk of active tuberculosis is greatest
soon after infection occurs
 Contacts of infectious cases are likely to
have been infected recently
 Treatment of those found to have a
positive tuberculin skin test will reduce the
likelihood of active tuberculosis
Treatment for LTBI: Evaluation
 Evaluate all potential LTBI treatment
candidates for active TB
 Identify those who have been treated
previously
 Identify those with contraindications to
treatment for LTBI (prior allergic
reactions, severe unstable liver disease)
 Identify co-morbid conditions and other
medications being used
ISTC Standard 19
 Children <5 years of age and persons
of any age with HIV infection who are
close contacts of an infectious index
patient and who, after careful evaluation,
do not have active tuberculosis, should
be treated for presumed latent TB
infection with isoniazid
Treatment for LTBI: Priorities
 Children <5 years
of age
 Persons with
HIV infection
 Persons with other
immunocompromising
conditions
 Close contacts of highly infectious index case
 Persons with other conditions that increase risk
(example: silicosis)
Other Treatment Considerations
 “Window-period” prophylaxis – treatment
(usually INH) given to high risk contacts with
an initial negative TST during the period
following last contact until the follow-up TST
 Priorities for initiating window-period
prophylaxis include:
• Children <5 years of age
• Persons with HIV infection
 Exposure to drug resistant TB – consult an
expert in the management of drug resistant TB
Follow-up
 All Contacts found to have latent TB
infection (LTBI) and started on treatment
should receive monthly visit by a nurse or
physician
 MDR-TB exposure – seek expert
consultation; follow-up for 2 years post
exposure
Contact Investigation Case Study
Part 4
Step 7: Evaluate C.I. Activities
 Management of care and follow up of TB
case and contacts
 Epidemiologic analysis of the
investigation in progress to allow
prioritization of program activities and
resources
 Program evaluation—measure how well
objectives are being met
Deciding Whether to Expand Testing
Evidence of Recent Transmission:
 Infection in a child (<5 years of age)
 TST converters
 Secondary case
 TB disease in any contact assigned a low
priority
Contact Investigation Case Study
Part 5
Summary: ISTC Standards Covered*
Standard 18: All providers of care for patients with
TB should ensure that persons who are in close
contact with patients who have infectious TB
are evaluated and managed in line with
international recommendations. The highest
priority contacts for evaluation are:
 Persons with symptoms suggestive of tuberculosis
 Children aged <5 years
 Contacts with known or suspected
immunocompromise, particularly HIV infection
 Contacts of patients with MDR/XDR tuberculosis
 Other close contacts are a lower priority group
* Abbreviated versions
Summary: ISTC Standards Covered* (2)
Standard 19: Children <5 years of age and
persons of any age with HIV infection who
are close contacts of an infectious index
patient and who, after careful evaluation,
do not have active tuberculosis, should be
treated for presumed latent tuberculosis
infection with isoniazid.
* Abbreviated versions
Summary
 Between 4 - 5 % of household contacts of new
cases will be found to have active TB and up to
50% may have LTBI
 The likelihood of transmission relates directly to
the bacillary burden of the index case
 Environmental factors also play an important
role
 Priorities for evaluation include children <5
years of age, persons with HIV infection, and
highly exposed contacts
 Treatment is indicated for high priority contacts
with LTBI and during the “window period”