Transcript RTMCC Medical Consultation

CDC Guidelines for Use of
QuantiFERON®-TB Gold Test
Philip LoBue, MD
Centers for Disease Control and Prevention
Division of Tuberculosis Elimination
Outline
• Where to find guidelines
• Recommendations for QFT-G use
• Guidance for follow up of
•
•
– Positive test result
– Negative test result
– Indeterminate test result
Special situations
– Contact investigation
– Serial testing (e.g., occupational)
Future research needs
Where Can You Find the Guidelines?
• Print: Guidelines for Using the
•
QuantiFERON®-TB Gold Test for Detecting
Mycobacterium tuberculosis Infection, United
States, MMWR, December 16, 2005 / Vol. 54 /
No. RR-15, pp. 49-54.
Internet:
http://www.cdc.gov/nchstp/tb/pubs/mmwrhtml
/maj_guide.htm
Recommendations for Use of QFT-G
QFT-G can be used in all
circumstances in which
the TST is used, including
• Contact investigations
• Evaluation of recent immigrants who have
•
had BCG vaccination
TB screening of health-care workers and
others undergoing serial evaluation for M.
tuberculosis infection
QFT-G usually can be used in place of
(and usually not in addition to) the TST
Follow up of Positive QFT-G
A positive QFT-G should prompt the same
health and medical interventions as a
positive TST result
• No reason exists to follow a positive QFT-G
•
•
with a TST
Persons with a positive QFT-G result should
be evaluated for TB disease before LTBI is
diagnosed
After TB has been excluded, treatment of
LTBI should be considered
Follow up of Negative QFT-G
The majority of healthy adults who have
negative QFT-G results are unlikely to
have M. tuberculosis infection and do not
require further evaluation
Cautions and Limitations
• As with a negative TST result, negative QFT-G results
•
•
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should not be used alone to exclude M. tuberculosis
infection in persons with symptoms or signs suggestive
of TB disease
The performance of QFT-G has not been determined in
persons who, because of impaired immune function
(e.g., HIV infection), are at increased risk for M.
tuberculosis infection progressing to TB disease
As with a negative TST result, negative QFT-G results
alone might not be sufficient to exclude M. tuberculosis
infection in immunocompromised persons
Limited published data document the performance of
QFT-G in children aged <17 years
Follow up of Indeterminate QFTG
An indeterminate QFT-G result does not
provide useful information regarding the
likelihood of M. tuberculosis infection
• Optimal follow up of persons with
•
•
indeterminate QFT-G results has not been
determined
Options are to repeat QFT-G with a new
blood sample, administer a TST, or do neither
Decision should be based on pre-test
likelihood of M. tuberculosis infection
Contact Investigations
For persons with recent contact to an
infectious TB patient, negative QFT-G
results should be confirmed with a repeat
test 8-10 weeks after exposure (end of
window period) as is recommended for a
negative TST
When “window prophylaxis” has been started
for high-risk contacts exposed to an infectious
TB patient, a negative QFT-G result at the end of
the window period should be interpreted in light
of all other clinical and epidemiologic data
• A full course of LTBI treatment should be
considered even with a negative result when the
rate of M. tuberculosis transmission to other
contacts is high or when a false-negative result is
suspected because of an immunocompromising
medical condition
Serial Testing
(e.g., Healthcare Workers)
In situations with serial testing for
M. tuberculosis infection (e.g.,
health-care workers), initial twostep testing (necessary for TST) is
not necessary for QFT-G
• In contrast to TST, there is no boosting with
QFT-G
Future Research Needs
• More data on performance of QFT-G in special
•
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populations (e.g., children, immunocompromised)
Longitudinal studies
– Subsequent TB disease incidence after LTBI has
been either diagnosed or excluded with QFT-G
– Length of time after infection for QFT-G test
result to become positive
– Changes in QFT-G results with therapy for TB
disease and LTBI
Economic evaluation and decision analysis
comparing QFT-G with TST
Questions?