A New Rapid Screening Method for Tuberculosis: TB-IGRA

Tuberculosis (TB) is a chronic infectious disease caused by the Mycobacterium tuberculosis complex (MTB). MTB can invade multiple organs in the human body, most commonly the lungs, but it can also affect the liver, skin, brain, bones, lymph nodes, and other tissues. Tuberculosis is a major global public health issue, posing a significant threat to public health. The primary route of transmission is airborne. Common clinical symptoms include fever, night sweats, fatigue, malaise, weight loss, anorexia, cough, sputum production, and hemoptysis.

Early detection and accurate diagnosis of active tuberculosis and latent TB infection (LTBI), along with timely initiation of preventive TB therapy, are crucial measures for reducing disease incidence and preventing further transmission. The TB-IGRA provides robust diagnostic data for cases of active pulmonary TB, as well as for situations where TB symptoms are atypical, the sensitivity of existing diagnostic methods is low, or extrapulmonary TB is difficult to detect. TB-IGRA enables early detection and treatment, making it an effective tool for rapid identification of infection sources and containment of TB spread.

Development of IGRA Technology

For over a century, the tuberculin skin test (TST) was the only available screening method for latent TB infection (LTBI). However, because the purified protein derivative (PPD) used in TST shares certain antigenic components with Bacillus Calmette–Guérin (BCG) vaccine strains and many environmental non-tuberculous mycobacteria (NTM), TST often exhibits a high false-positive rate, resulting in low diagnostic specificity.

In the 1990s, advancements in comparative genomics led researchers to identify a genomic segment missing in all BCG strains and most environmental mycobacteria, termed Region of Difference 1 (RD1). Two major proteins encoded by this region, Early Secreted Antigenic Target 6 (ESAT-6) and Culture Filtrate Protein 10 (CFP-10), are immunodominant antigens of M. tuberculosis. These proteins can stimulate the proliferation of antigen-specific T-cells and induce significant interferon-gamma (IFN-γ) secretion, playing a vital role in protective cellular immune responses and the establishment of long-term immune memory.

Thus, IGRA technology based on the specific stimulation of ESAT-6 and CFP-10 was developed. Studies have demonstrated that IGRA exhibits significantly higher sensitivity and specificity compared to TST. With continuous technological improvements, commercially available IGRA kits based on ELISA and ELISPOT platforms were successively launched. Due to its excellent diagnostic sensitivity and specificity, in 2011, the World Health Organization (WHO) recommended the use of IGRA as an alternative to TST for TB infection screening in low TB burden countries.

Advantages of TB-IGRA Technology

• TB-IGRA achieves a detection rate of over 85% for TB infections, making it suitable for the detection of latent infections and significantly enhancing early-stage detection capability.

• Use of M. tuberculosis-Specific Antigens: TB-IGRA eliminates cross-reactivity with BCG vaccination and can differentiate between pulmonary infections caused by non-tuberculous mycobacteria and pulmonary TB.

• In Vitro Testing with Whole Blood Samples: Both pulmonary and extrapulmonary TB can be detected safely without the need for invasive procedures.

• The system quantitatively reflects bacterial load, making it useful for monitoring treatment efficacy and latent TB infection status.

Clinical Applications of TB-IGRA

• Assists in the diagnosis of M. tuberculosis infection, including pulmonary TB, extrapulmonary TB, and latent TB infection, as well as in the assessment of anti-TB treatment efficacy.

• Used for TB infection screening among close contacts of TB patients and other high-risk populations.

• Applicable for TB infection screening in routine health examinations (e.g., occupational health checks, employment or school entry medical exams, infertility evaluations).

Hotgen's TB-IGRA Detection System

To meet the needs for early diagnosis of tuberculosis and detection of latent TB infection, Hotgen has launched a highly sensitive and specific TB-IGRA detection system. This system includes a chemiluminescence detection platform featuring the mono-test chemiluminescence detection MQ60 series and the fully automatic chemiluminescence analyzer C800, providing accurate and reliable detection results for TB infection and offering robust support for the early identification and effective control of tuberculosis.