Qiagen N.V has announced that two peer-reviewed studies indicate the potential additional clinical value for QuantiFERON-TB Gold Plus (QFT-Plus), the fourth-generation test using enhanced QuantiFERON technology to detect latent tuberculosis (TB) infection. Both studies focus on potential benefits of novel CD8+ T-cell stimulating antigens contained in QFT-Plus. A study at the Stanford University School of Medicine is the first publication describing the performance of QFT-Plus in healthcare workers, while a study at Japan’s National Hospital Organization Hokkaido Medical Center provides the first evidence for QFT-Plus as a potential monitoring aid during treatment of active TB.

“These studies add to a growing body of clinical evidence on QuantiFERON-TB Plus, suggesting added utility for our novel CD8+ T-cell technology. We have introduced QFT-Plus in more than 60 markets since 2015 to aid in tuberculosis control by screening at-risk populations for latent TB infection,” said Dr. Masae Kawamura, Senior Director, TB Medical and Scientific Affairs, at QIAGEN. “The unique ability of QFT-Plus to measure CD8+ immune response has led the World Health Organization to suggest that the new test offers potential for identifying patients at greater risk of progressing to active TB. A number of clinical studies are underway to explore broader applications based on the CD8+ capability, although regulatory approvals to date focus on the effectiveness of QFT-Plus in detecting latent TB infection.”

As the world’s leading interferon gamma release assay (IGRA), QuantiFERON technology is a faster, less labor-intensive and more accurate latent TB test compared to the century-old tuberculin skin test. QuantiFERON-TB Gold (QFT), the third-generation assay, measures the immune response with antigens that primarily elicit a CD4+ T-cell response. A positive result indicates infection, and guidelines recommend treatment of latent TB to prevent progression to active disease. QuantiFERON-TB Gold Plus, the fourth generation, builds on this foundation by adding proprietary CD8+ antigens, as well as workflow improvements.

In the Stanford study, published by the Journal of Clinical Microbiology, researchers screened 989 US healthcare workers (HCWs) at low risk for tuberculosis infection with both QFT-Plus and QFT. Comparing results showed agreement of 95.6% between the two tests. Researchers found they could reduce the positivity rate in risk-free HCWs population by applying a “conservative” reading where only a positive QFT-Plus result in both antigen tubes counted as a positive, thereby utilizing a positive immune response to both the CD4+ and CD8+ antigens to confirm a positive result. The authors say that using QFT-Plus with a double-positive interpretation strategy could increase specificity in screening low-risk healthcare workers, limiting unnecessary follow-up treatment and reducing costs of TB management.

In the Japanese study, a research letter published by the European Respiratory Journal, the Hokkaido Medical Center in Sapporo used QuantiFERON-TB Plus to assess 38 patients being treated for active pulmonary TB. They were tested at the start of their tuberculosis treatment, and after three and six months. Using QFT-Plus, the researchers compared measurements of the patients’ CD4+ (TB1 antigen tube) and CD8+ (TB2-TB1 antigen tubes) responses and found that both declined significantly in the first three months. Between three and six months, the CD8+ response was more effective at measuring further containment of the infection. The researchers suggest the potential use of QFT-Plus to monitor the ongoing progress of TB treatment.

Tuberculosis is a contagious bacterial infection spread primarily through the air, such as by coughing from patients with the active pulmonary form of TB. About 10.4 million new cases of active TB disease and 1.8 million deaths were reported by the World Health Organization for 2015. About one-third of people worldwide have latent TB infection, in which the bacterium infects a person but does not cause symptoms. About 5-10% of those individuals with latent TB, if untreated, will progress to active disease – so screening and treatment for latent infection play a growing role in global tuberculosis control efforts.

QIAGEN partners with governments and health organizations around the world to fight tuberculosis and continues to develop innovative new technologies. Use of QuantiFERON-TB screening solutions continues to grow rapidly, with a total of more than 30 million tests conducted so far. QFT-Plus is approved with CE-IVD marking in Europe and has been submitted to the US Food and Drug Administration (currently available for research use only in the United States).