By Rachel Pomerance
PALO ALTO, CA — As a physician with Stanford University’s emergency department and occupational health center, Wendy Thanassi, MD, got an early look at usage of Interferon-Gamma Release Assays (IGRA), revolutionary new blood tests that screen for tuberculosis.
– Wendy Thanassi, MD
So in 2009, when she became chief of occupational services at the VA Palo Alto Health Care System, Thanassi advised supplanting the traditional tuberculin skin test (TST) with the third-generation QuantiFERON test, known as QuantiFERON-TB Gold In-Tube (QFT-GIT). It is one of two types of IGRA available for use at VA; the other is the T-SPOT.TB test, which became available on the Federal Supply Schedule for Medical Laboratory Testing and Analysis Services in November.
“We all knew that [IGRAs] are a better test than the TST. We knew that it would provide us more accurate information,” Thanassi said, praising her director’s office for jumping on the opportunity to pursue the first advancement in TB testing in more than a century.
Now that the Palo Alto VA has administered 15,000 of the blood tests, Thanassi has the data to back up a move she called “absolutely invaluable.”
Results such as hers have the VA gearing up for a transition to TB testing through the blood tests and weighing the advantages of each type. Available IGRAs include the QuantiFERON tests (QFT), which can be handled by an internal lab, and the T-SPOT.TB, which requires considerably less blood and is more sensitive in certain situations but must be sent away for results. Both are considered far more efficient than the skin tests, notorious for inconsistencies in patient compliance and clinical interpretation as well as false positives for those vaccinated for tuberculosis.
Earlier this year, Under Secretary of Health Robert Petzel, MD, dispatched a letter on the subject to the publication distribution list of the Veterans Health Administration.
“IGRAs are cost-effective tests that can be used in place of TSTs in all situations in which the CDC recommends TST,” Petzel stated. “Further head-to-head comparison studies need to be performed to determine if one IGRA is more sensitive or specific than another.”