Lancet study finds that Qiagen's Quantiferon estimates lower rate of TB in China than the traditional test
Qiagen ($QGEN) pointed to a head-to-head comparison study in The Lancet showing that its Quantiferon-TB Gold tuberculosis test could be more accurate at detecting tuberculosis than the traditional tuberculin skin test (TST), which the company said is overestimating the prevalence of the disease in China.
The study screened more than 21,000 people in China for latent tuberculosis. The TB infection rate was 18.8% using the company's QFT, compared to 28% using the skin test, the release says. Qiagen says the skin test overstates the TB rate due to several factors, most notably the prevalence of BCG vaccination for prevention of the disease among children.
The U.S. Centers for Disease Control and Prevention (CDC) does not recommend the BCG vaccination in the U.S. and warns that its effectiveness varies in adults and it has the potential to interfere with the skin test. However, the World Health Organization recommends the vaccination in many countries, including China, to protect newborns.
Qiagen says the results of its Quantiferon interferon-gamma release assay (IGRA) were not influenced by prior BCG vaccination. In addition, the CDC stresses that "reliable administration and reading of the skin test requires standardization of procedures, training, supervision, and practice."
Results of the skin test are determined by the size in millimeters of the area of swelling that forms in the forearm 48 to 72 hours after an injection of tuberculin purified protein derivative, according to the CDC. Quantiferon, in contrast, is a blood test; its results are determined by clinicians in a laboratory.
Up to 10% of those with latent TB will develop an active and contagious version of the infection, according to the release.
"The study shows that historical estimates of latent TB infection in China, as high as 44.5% of the population, were overinflated by TST as compared to IGRA," said Dr. Lee Reichman, the executive director of the Global Tuberculosis Institute at the New Jersey Medical School at Rutgers University. "While most TB control efforts in China so far have not focused on prevention, the research findings can guide policymakers to focus appropriate preventive interventions on the right people, which is a smaller group and based on the risk factors found in the study."
Those vulnerable groups are the elderly, smokers, and people with close contact to an active TB patient, The Lancet study finds.
In its year-end earnings report, Qiagen said Quantiferon exceeded $100 million in sales, representing a double-digit growth rate at constant exchange rates.
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