What is QuantiFERON – TB Gold?
For many years the tuberculin skin test (TST) or PPD has been the basic screening test for detecting latent tuberculosis infection (LTBI) in healthcare workers. Limitations include the need to measure the response (induration) within 48-72 hours after the application of the TST as well as inaccuracies and errors in determining if the response meets the definition of a positive TST. In 2005, the Food and Drug Administration approved an in vitro laboratory diagnostic test to diagnose LTBI. Guidelines for using QuantiFERON – TB Gold are available from the Centers for Disease Control and Prevention (CDC) at the CDC Guidelines for Using the QuantiFERON - TB GOld Test website.
Use of a blood test for screening healthcare workers for LTBI requires a grant of program flexibility from the California Department of Health Services, Licensing and
Certification, since the TST is required by regulation (California Code of Regulations, Title 22, all chapters – see below). Use of QuantiFERON – TB Gold for screening patients, residents or clients on admission to a health care facility does not require program flexibility because the test method is not specified in the regulation. Therefore the facility may choose either the QuantiFERON – TB Gold or the TST for patient, resident and client LTBI screening.
Requirements for Submitting a Request for Program Flexibility to Use QuantiFERON – TB Gold
- The facility must submit a letter to the Licensing and Certification district office with jurisdiction over the facility signed by the hospital administrator or designee requesting that program flexibility be granted for the use of QuantiFERON –TB Gold for LTBI healthcare worker screening.
- The facility must submit a policy specifying that QuantiFERON – TB Gold is to be used for screening healthcare workers for LTBI. The policy must comply with current standards of practice for LTBI screening as defined by the California Occupational Safety and Health Administration (Cal-OSHA) for new employee, annual and post-exposure testing. The policy must stipulate that QuantiFERON – TB Gold will be used exclusively for new employee LTBI screening or, in addition, the test will also be used for annual and post-exposure screening.
- The policy must include a statement that employees will be informed in writing of the limitations of using QuantiFERON – TB Gold as defined by most current recommendations by the Centers for Disease Control and Prevention (CDC) or the California Tuberculosis Controllers Association (if applicable). The CDC currently identifies the following limitations:
- As with a negative TST result, negative QuantiFERON – TB Gold results should not be used alone to exclude M. tuberculosis infection in persons with symptoms or signs suggestive of TB disease. The presence of symptoms or signs suggestive of TB disease increases the likelihood that M. tuberculosis infection is present, and these circumstances decrease the predictive value of a negative QuantiFERON – TB Gold or TST result. Medical evaluation of such persons should include a history and physical examination, chest radiograph, bacteriologic studies, serology for human immunodeficiency virus (HIV), and, when indicated, other tests or studies.
- The performance of QuantiFERON – TB Gold, in particular its sensitivity and its rate of indeterminate results, has not been determined in persons who, because of impaired immune function, are at increased risk for M. tuberculosis infection progressing to TB disease. Impaired immune function can be caused by HIV infection or acquired immunodeficiency syndrome (AIDS); current treatment with immunosuppressive drugs including high-dose corticosteroids, tumor necrosis factor-alpha (TNF-a) antagonists, and drugs used for managing organ transplantation; selected hematologic disorders
(e.g., myeloproliferative disorders, leukemias, and lymphomas); specific malignancies (e.g., carcinoma of the head, neck, or lung); diabetes; silicosis; and chronic renal failure.
Each of these conditions or treatments is known or suspected to decrease responsiveness to the TST, and they also might decrease production of IFN-g in the QFT-G assay. Consequently, as with a negative TST result, negative QuantiFERON – TB Gold results alone might not be sufficient to exclude M. tuberculosis infection in these persons.
- Published data are relatively limited concerning the use of QuantiFERON – TB Gold among persons recently exposed to TB (e.g., contacts) and other populations at high risk for LTBI. No published data document the performance of QFT-G in children aged <17 years.
- With any of the testing methods, persons who have a negative test result can still have LTBI. Those who have a negative result but who are likely to have LTBI and who are at greater risk for severe illness or poor outcomes if TB disease occurs might need treatment or closer monitoring for disease. Potential examples include close contacts who are aged <5 years, those who are immunocompromised because of HIV infection, or those who will undergo treatment with TNF-a antagonists (which increase the risk for progression from LTBI to TB disease)”.
For questions regarding this letter, please contact Patricia DeWan-Duran at (916) 440-7360.
Original Signed by Patricia DeWan-Duran for Brenda Klutz
Brenda G. Klutz
Attachment: Title 22 Chapters for the Use of TST (PPD) for Screening Employees for LTBI