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| |  Blood Test Effective in Latent TB Screening: Presented at CHEST By John Gever CHICAGO, IL -- October 24, 2007 -- A blood test for latent tuberculosis (TB) is superior in key ways to conventional skin testing and could soon become the standard screening method, according to research presented here at CHEST 2007, the annual meeting of the American College of Chest Physicians. The test, called QuantiFERON(R)-Gold, measures interferon-gamma released from T cells that were previously exposed to TB-causing mycobacteria. It can be performed on whole blood samples and can deliver results within 1 day. The test, which is approved for sale in the United States and elsewhere, can detect TB infections in the latent phase. The current standard is the tuberculin skin test (TST), which takes substantially longer to produce results and gives positive findings in people who have previously received Bacille Calmette-Guérin (BCG) vaccination and have never been TB-infected. Susan Marantz, MD, MPH, Medical Director, Tuberculosis Prevention and Control, Cook County Department of Health, Oak Park, Illinois, United States, presented a retrospective 1-year analysis of her department's use of the QuantiFERON test on foreign-born people. The department serves a large immigrant population from Latin America, Africa, Asia and Eastern Europe -- where TB is endemic. In her presentation on October 22, Dr. Marantz said her department has been administering some 30,000 TSTs annually, with about 120 active infections typically found, three quarters of which have been in foreign-born individuals. In early 2006, the department switched to QuantiFERON as the screening test for latent infections. The analysis covered people of foreign birth aged 16 to 49 years, and excluded those with HIV or other immunocompromising conditions. Patient records were reviewed for risk factors, treatments, outcomes, demographic data, and reasons for screening. Nearly 2,900 QuantiFERON tests were performed during the study year, of which 20% were positive. Workplace requirements were the most common reason for being screened (42%) while contact with an infected person was the least common (5%). Treatment was provided to 344 of the 445 people with positive results, although 37% of those failed to complete the prescribed treatment. Those that did not receive treatment were notified that they had latent infections but "didn't bother showing" at the clinic, Dr. Marantz said. Based on informal discussions with the service's clientele, reasons for not seeking treatment range from pregnant women's reluctance to take medication to belief that everyone from their homelands tests positive for TB (mostly among Eastern European clientele). Among the approximately 2,300 patients with negative QuantiFERON results, nearly 300 had positive TST findings. The latter were considered false positives, Dr. Marantz indicated. Since in the absence of QuantiFERON testing these people would have been offered treatment, the use of QuantiFERON resulted in cost savings. Overall, the number of latent TB infections detected in suburban Cook County decreased by approximately 30% from earlier years, attributable at least in part to QuantiFERON testing, Dr. Marantz said. By negotiating "very aggressively" with the university laboratory that conducted the tests, her department paid $25 per test, Dr. Marantz said, making it affordable for routine screening. "We will probably go to all [QuantiFERON] in the next couple years," she said.
[Presentation title: Latent Tuberculosis Infection Screening of Foreign Born Patients Using Quantiferon-Gold (QFT-G) in Suburban Cook County TB Clinics in Illinois. Abstract 928]
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