Self-Study Modules on Tuberculosis
Module 6: Contact Investigations for Tuberculosis
Decision About Priority of Contacts
To use time and resources wisely, the contact investigation should
be focused on the high-priority contacts, the contacts
who are most at risk for developing TB infection or TB disease.
In other words, the highest priority for testing should be given
- Contacts who are most likely to be infected,
based on the risk that M. tuberculosis was transmitted
- Contacts who are at high risk of developing disease
if infected, including young children less than 4 years
of age, HIV-infected and other immunosuppressed persons, and persons
with certain medical conditions (Table 6.6).
Contacts Most Likely to be Infected
These are people who had close, regular, prolonged contact with
the TB patient while he or she was infectious, especially in small,
poorly ventilated places. These contacts are classified as close
contacts, and usually include people who have shared a
house or room with the patient or spent time with the patient frequently
during the period of infectiousness. Contacts with less intense,
less frequent, or shorter durations of contact to the TB patient
are classified as other-than-close contacts, and
they generally should be given a lower priority for testing.
It is not always possible to easily classify contacts as "close"
or "other-than-close" right away because the health care worker
may continue to receive information as the contact investigation
continues. Contacts who are considered to have the most exposure
to the patient should receive highest priority and contacts who
have the least exposure should be given the lowest priority based
on available information. The priority given to a contact can change
over time as new information is collected and old information is
updated and revised. Decisions about the prioritization of contact
investigations should be made by supervisory and clinical staff.
- A family member who lives in the same home or apartment as the
patient is a close contact; a family member or friend who lives
elsewhere but visits for a few hours every other week is an other-than-close
- Likewise, the coworker of an infectious TB patient who works
alongside the patient each day for several hours in a small restaurant
kitchen is a close contact; a delivery person who brings produce
to the restaurant 2 days a week and is exposed to the patient
for 15 minutes each time is an other-than-close contact
- A person who drinks with the patient at the local bar for a
few hours three times a week is a close contact; a person who
plays pool with the patient two times each month is an other-than-close
A very low priority contact would be someone who met the patient
once or twice briefly during the period of infectiousness. If there
is evidence that close contacts have been infected, then other-than-close
contacts may be tested.
By using the factors included in Table 6.6
to assess a contact's risk of becoming infected, it should be possible
to define a group of close contacts: those persons who are most
likely to have been infected.
Contacts at High Risk of Developing TB Disease if Infected
Some conditions, such as HIV infection, immunosuppressive therapy,
and low body weight, increase the risk that TB infection will progress
to TB disease (see Module 1, Transmission
and Pathogenesis of Tuberculosis). Contacts with these conditions
should be given high priority for TB testing, regardless of whether
they are close contacts or other-than-close contacts. Young children
less than 4 years of age should also be given high priority for
testing, because they can develop serious forms of TB disease very
quickly after infection.
The high-priority contacts for testing are summarized in Table
High-Priority Contacts for Testing
|Contacts Most Likely
to Be Infected
|Contacts at High Risk of Developing
TB Disease Once Infected
- Contacts exposed to patients with a high degree of infectiousness
based on the following factors:
- Laryngeal or pulmonary TB
- AFB sputum smear-positive
- Cavitary disease on chest x-ray
- Positive culture for Mycobacterium tuberculosis
- Contacts exposed to patients in
- Small or crowded rooms
- Areas that are poorly ventilated
- Areas without air-cleaning systems
- Contacts who
- Frequently spend a lot of time with the patient
- Have been physically close to the patient
| Contacts who are young children less than
4 years of age
- Contacts with any of these conditions:
- HIV infection
- Injection of illicit drugs
- Diabetes mellitus
- Prolonged corticosteroid therapy
- Immunosuppressive therapy
- Certain types of cancer
- Severe kidney disease
- Certain intestinal conditions
- Low body weight (10% or more below ideal)
|Study Questions 6.26-6.28
contacts should be classified as close contacts and are
most likely to be infected?
6.27. Which contacts are at high risk of developing TB
disease if infected?
6.28. Which contacts should be considered high-priority
contacts for testing?
|Case Study 6.6
You are in charge of the contact investigation for
35-year-old Hector Gonzalez, who is strongly suspected of
having pulmonary TB disease. One week ago, Hector came to
the health department complaining of night sweats, a 10-pound
weight loss, and a persistent cough that has lasted about
a month. His sputum smears were positive for AFB, and he started
four-drug treatment for TB disease.
When you interviewed Hector 3 days ago, you found out that
he lives with his 32-year-old wife, Mimi; two sons, Luis,
2, and Javier, 4; and his mother-in-law, Alma, 65. Hector's
cousin, Henry, has stopped by the house a few times in the
past month. Hector informed you that Henry has been HIV
positive for 2 years.
Hector rides to work every day with his friend Joe. The
ride lasts about half an hour. Hector works in a car assembly
plant. About 100 employees work in the main room with Hector,
but the room is divided into several sections. There are
20 people in Hector's section, and 4 of these people are
assigned to work closely with Hector. Hector eats lunch
outside every day with these 4 coworkers.
About twice a week and on weekends, Hector goes to a small
neighborhood bar located in the basement of a building.
At the bar, Hector spends most of the time talking to the
- Which contacts would you consider close contacts?
- Which contacts would you evaluate first (the high-priority
Evaluation of Contacts
What Does the Evaluation Include?
Evaluation of TB contacts should be done in an orderly manner,
starting with the highest-priority group of contacts. Contacts should
be evaluated for LTBI and TB disease. This evaluation includes at
- A medical history and
- A Mantoux tuberculin skin test (unless there is a previous documented
For immunosuppressed contacts or contacts who are under 4 years
of age, the evaluation should also include a chest x-ray, regardless
of skin test result, because of the possibility of a false-negative
reaction to the tuberculin skin test and risk of early progression
to TB disease if infected (see Module
3, Diagnosis of Tuberculosis Infection and Disease).
In addition, any contact who has TB symptoms should be given both
a chest x-ray and a sputum examination.
Contacts should be asked about their
- History of TB infection or disease
- Documented previous tuberculin skin test results
- Previous treatment for TB infection or disease
- Previous exposure to TB
- Risk factors for developing TB disease
- Current symptoms of TB
Contacts should be questioned about risk factors for HIV and offered
counseling and testing if their HIV status is not known and they
are at risk.
Mantoux Tuberculin Skin Test
All high-priority contacts should be given a Mantoux tuberculin
skin test; a reaction of 5 or more millimeters of induration
is considered positive for contacts. Some contacts may
indicate that they have been vaccinated with BCG. BCG (bacillus
Calmette-Guérin) is a vaccine for TB disease that is used
in developing countries. However, it is rarely used in the United
States because studies have shown that it is not completely effective.
People who have been vaccinated with BCG may have a positive reaction
to the tuberculin skin test even if they do not have TB infection.
This is called a false-positive reaction. There is no reliable way
to distinguish a positive tuberculin reaction caused by a vaccination
with BCG from a reaction caused by true TB infection. During
a contact investigation, people who have a positive reaction to
a tuberculin skin test should be further evaluated for TB disease,
regardless of whether or not they were vaccinated with BCG
(see Module 3, Diagnosis of Tuberculosis
Infection and Disease).
Contacts who have a previously documented positive tuberculin skin
test should not receive another skin test, but should be evaluated
for symptoms of TB disease, and asked about any history of treatment
for TB infection or TB disease, and may need a chest x-ray. Depending
on the results of the evaluation, some of these contacts may be
candidates for treatment for LTBI or TB disease.
Contacts who are skin tested less than 10 to 12 weeks after their
last exposure to a patient with infectious TB may have a false-negative
reaction, because they may not yet be able to react to the tuberculin.
It takes 2 to 12 weeks after TB infection for the body's immune
system to react to tuberculin. For this reason, contacts of someone
with infectious TB disease who have a negative initial skin test
reaction should be retested 10 to 12 weeks after the last contact
with the person who has TB disease. The time span between the date
of an initial skin test with a negative reaction and the date that
is 10 to 12 weeks after exposure is called the window period.
After the window period has ended, a repeat skin test should
be administered to each contact who had an initial negative reaction.
For example, a contact whose last exposure to TB occurred on July
1 has an initial negative skin test reaction on August 1, only 4
weeks after his or her exposure. This contact should have a repeat
test between September 15 and October 1, or 10 to 12 weeks after
exposure. The contact's window period is from August 1 through October
1 (Figure 6.7).
As with adults, children should be retested 10 to 12 weeks after
exposure. Infants under 6 months of age may have a false-negative
skin test reaction because their immune systems are not yet able
to react to tuberculin. Infants need careful clinical evaluation.
Figure 6.7 This is a sample time line demonstrating how to
determine the window period.
All contacts who have a positive skin test reaction with an induration
greater than 5 mm or who report any TB symptoms should be given
a chest x-ray. The purpose of the chest x-ray is to rule out the
possibility of TB disease and to look for signs of old TB disease
before treatment for LTBI is started. The results of a chest x-ray
alone cannot confirm that a person has TB disease; smear and culture
evaluations are necessary if the chest x-ray results are abnormal.
Certain contacts should have a chest x-ray to evaluate for TB disease
at the same time the initial skin test is done,
including those who
- Have TB symptoms
- Are HIV-infected or have other immunosuppressed conditions
- Are under 4 years of age
Because of their high risk of quickly developing TB disease, HIV-infected
and other immunosuppressed contacts and young children may already
have TB disease by the time of the contact investigation.
In addition, if many close contacts have a positive skin test reaction,
other high-risk close contacts may be considered for treatment for
LTBI even if the initial skin test reaction is negative. This is
especially true if the initial skin test was given during the window
period or if a false-negative reaction is suspected. Such persons
need a chest x-ray to exclude the possibility of TB disease before
they begin treatment for LTBI.
Any contact who has an abnormal chest x-ray or who has TB symptoms
should have three sputum specimens collected on different days for
smear and culture examination, regardless of his or her tuberculin
skin test reaction. The results of the smear examination can be
used to help determine the person's infectiousness, although a negative
smear does not rule out the possibility of TB disease (see
Module 3, Diagnosis of Tuberculosis Infection and Disease).
|Study Questions 6.29-6.32
all high-priority contacts, what procedures should be done
6.30. In what situation should tuberculin testing of contacts
6.31. Which contacts should be given a chest x-ray?
6.32. What is the purpose of a sputum examination and when
should one be done?
|Case Study 6.7
The high-priority contacts you identified in Case
Study 6.6 for Hector Gonzalez, a patient suspected of having
TB disease, were
- Household members: Mimi (wife), Luis and Javier (sons),
- Close friend: Joe
- Four coworkers who work closely with Hector
- Bartender at the local bar
- Hector's cousin Henry, who has HIV infection
These contacts (a total of 11) are being tested by the
contact investigation team. Five weeks have passed since
the contacts were last exposed to Hector while he was infectious.
- Which contacts should be evaluated with a medical history
and skin test? Which contacts also should be given a chest
None of the contacts had TB symptoms. The skin test results
were as follows:
Newly identified positive reaction: Mimi,
32 (11 mm); Javier, 4 (13 mm)
Negative reaction: Luis, 2 (0 mm); Alma,
65 (3 mm); Joe (3 mm); Henry, HIV+ (0 mm); Coworker A (2
mm); Coworker B (0 mm); Coworker C (0 mm); Coworker D (3
mm); the bartender (0 mm)
- What follow-up testing and treatment are needed for
contacts with a positive skin test reaction?
- Should any follow-up testing or treatment be given to
contacts with a negative skin test reaction at this time?
- Which contacts should receive a repeat skin test? When
should the repeat test be performed?
Treatment and Follow-up for Contacts
The following contacts should be evaluated for treatment for LTBI:
- Contacts who have a positive tuberculin skin test reaction and
no evidence of TB disease
- High-risk contacts who have a negative tuberculin skin test
reaction, such as children under 4 years of age, HIV-infected
people, and other high-risk contacts who may develop TB disease
very quickly after infection
Contacts recently infected with M. tuberculosis are a
high-priority group for treatment for LTBI because they are at high
risk of developing TB disease. (The highest risk of developing TB
disease is in the first 2 years after infection.)
Some contacts who have a negative tuberculin skin test reaction
(less than 5 millimeters of induration) should be evaluated for
treatment for LTBI, after TB disease has been ruled out. These contacts
include children under 4 years of age, HIV-infected and other immunosuppressed
people, and others who may develop TB disease very quickly after
High-risk contacts (including children under 4 years of age) with
a negative skin test reaction less than 10 to 12 weeks after their
exposure should start treatment for LTBI and be retested after the
window period ends. This is called window period prophylaxis.
If the second skin test reaction is negative, treatment for LTBI
is usually stopped. If the second skin test reaction is positive,
they should continue taking treatment for LTBI. Infants younger
than 6 months of age should be evaluated as discussed previously.
HIV-infected contacts or other immunosuppressed contacts may be
given a full course of treatment for LTBI, regardless of their skin
test results, because of the possibility of a false-negative skin
test result. This is particularly true when there is evidence of
transmission to other contacts with a similar degree of exposure
and likelihood of a false-negative skin test result.
Contacts who have a positive sputum smear or chest x-ray results
suggestive of current TB disease should begin treatment for TB disease
(see Module 4, Treatment of Tuberculosis
Infection and Disease).
Testing, treatment, and follow-up for contacts are summarized in
Figures 6.8, 6.9, and 6.10, which present diagrams for
- Contacts 4 years of age or older
- Contacts under 4 years of age
- Immunosuppressed contacts
The following diagrams are presented as guides only, and are not
meant to substitute for careful consideration of each contact's
risk of exposure, infection, and progression to disease. It is important
to always keep in mind the ultimate goal of the contact investigation:
treatment for contacts with LTBI or TB disease. Throughout the process
of testing, treatment, and follow-up, appointment keeping and adherence
to prescribed therapy should be monitored closely (see
Module 9, Patient Adherence to Tuberculosis Treatment, for further
Figure 6.8 This a flow chart depicting the decisional analysis
for the testing, treatment, and follow-up for contacts 4 years of
age or older.
Figure 6.9 This a flow chart depicting the decisional analysis
for the testing, treatment, and follow-up for contacts under 4 years
Figure 6.10 This a flow chart depicting the decisional analysis
for the testing, treatment, and follow-up for immunosuppressed contacts.
|Study Questions 6.33-6.34
contacts should be evaluated for treatment for LTBI?
6.34. What is window period prophylaxis and when should
it be used?