Director of Medical Affairs, QIAGEN
TB remains one of the world’s most common infectious diseases worldwide. New technology can diagnose it more efficiently and accurately.
Canadians are well acquainted with COVID-19, an infectious disease that can have serious consequences, but it’s not the only one that needs to be addressed. Tuberculosis (TB) remains one of the most common infectious diseases in the world, among the top 10 causes of death worldwide. According to the WHO, 10 million people globally were infected in 2019 and 1.4 million died from this airborne and highly contagious disease caused by bacteria (Mycobacterium tuberculosis). The latest data from Health Canada showed the rate of active TB at 4.9 per 100,000 population.
The good news is that TB is curable and preventable, especially with early detection. But TB testing has slowed during the COVID-19 pandemic, risking years of progress in the global fight to end the TB epidemic. As a result, the WHO is urging health authorities to ensure that TB prevention, diagnosis, treatment and care services are maintained in tandem with the COVID-19 response.
“Achieving ambitious End TB strategy goals, especially in the COVID-19 era, will not be possible without universal access to latent TB screening and offering TB preventive therapy for people from high-risk groups including household contacts, patients on dialysis and those starting on anti-TNF therapy,” says Vladyslav Nikolayevskyy, Director of Medical Affairs at QIAGEN, a German provider of sample and assay technologies for molecular diagnostics, applied testing, and academic and pharmaceutical research.
Understanding the connection between biologics and TB
Active TB causes symptoms like chest pain, coughing, fever and night sweats, while latent TB may lie dormant in the body without causing illness. For those patients with inflammatory diseases who will be treated with biologic agents, being tested for TB beforehand is critical. Anti-TNF (tumor necrosis factor) therapies may be used to treat conditions such as rheumatoid arthritis, inflammatory bowel disease (like Crohn’s and ulcerative colitis) and psoriasis. However, one of the common adverse effects of these types of medications is an increased risk of reactivation of latent TB and progression to active TB disease.
For more than a century, a tuberculin skin test (TST) has been used to diagnose TB. It requires an injection and two appointments with a clinician. As well, the results may be affected among those who have previously received the Bacillus Calmette–Guérin (BCG) vaccine (commonly used to prevent the worst effects of childhood TB in high-risk countries), resulting in more false positives and missed diagnoses.
New testing technology leads to more accurate results
Over the last 15 years, TB testing has taken a giant leap forward, thanks to advancements in technology. Blood tests, known as interferon-gamma release assays (IGRAs), have been introduced by companies such as QIAGEN, which offers QuantiFERON-TB Gold Plus (currently available in Canada). These tests have improved the accuracy of TB detection. They use an IGRAs to measure the T cell immune response to mycobacterium tuberculosis (MTB).
These IGRA blood tests offer numerous advantages over skin tests. They require just a single patient visit to their doctor and a small sample of blood. IGRAs are also not affected by previous BCG vaccination. IGRAs have been recognized by organizations like the CDC, Health Canada and the World Health Organization, due to their accuracy, convenience and cost-effectiveness since they don’t require multiple medical appointments and can reduce false positives. Single-visit testing can be particularly valuable during the COVID-19 pandemic – reducing unnecessary patient visits and the potential of COVID-19 exposure at clinics and hospitals.
“IGRAs offer huge advantages over TST due to their accuracy and convenience for patients, laboratory personnel and doctors. Its high specificity translates into significantly fewer patients needed to treat compared to TST meaning it’s a cost-effective technology,” says Nikolayevskyy.
“Disclaimer: The performance of QuantiFERON-TB Gold Plus test has not been extensively evaluated with specimens from individuals who have impaired or altered immune functions, such as those who have transplantation managed withimmunosuppressive treatment or others who receive immunosuppressive drugs (e.g., corticosteroids, methotrexate, azathioprine, cancer chemotherapy).”