1. CDC Guidelines for Use of QuantiFERON®-TB Gold Test
Philip LoBue, MD
Centers for Disease Control and Prevention
Division of Tuberculosis Elimination

2. 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

3. 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
Internet:

4. Recommendations for Use of QFT-G

5. 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

6. QFT-G usually can be used in place of (and usually not in addition to) the TST

7. Follow up of Positive QFT-G

8. 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

9. Follow up of Negative QFT-G

10. The majority of healthy adults who have negative QFT-G results are unlikely to have M. tuberculosis infection and do not require further evaluation

11. Cautions and Limitations
As with a negative TST result, negative QFT-G results 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

12. Follow up of Indeterminate QFT-G

13. 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

14. Contact Investigations

15. 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

16. 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

17. Serial Testing (e.g., Healthcare Workers)

18. In situations with serial testing for M. tuberculosis infection (e. g
In situations with serial testing for M. tuberculosis infection (e.g., health-care workers), initial two-step testing (necessary for TST) is not necessary for QFT-G
In contrast to TST, there is no boosting with QFT-G

19. Future Research Needs

20. More data on performance of QFT-G in special populations (e. g
More data on performance of QFT-G in special 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

21. Questions?