From the Guidelines
Tuberculosis (TB) markers are biological indicators used to detect, diagnose, and monitor TB infection and disease, including tuberculin skin tests (TST) and interferon-gamma release assays (IGRAs) like QuantiFERON-TB Gold and T-SPOT.TB for detecting latent TB infection, as well as sputum smear microscopy, culture tests, and nucleic acid amplification tests (NAATs) for active TB diagnosis. The most common TB markers include:
- Tuberculin skin tests (TST)
- Interferon-gamma release assays (IGRAs) like QuantiFERON-TB Gold and T-SPOT.TB for detecting latent TB infection
- Sputum smear microscopy, culture tests, and nucleic acid amplification tests (NAATs) like GeneXpert MTB/RIF for active TB diagnosis
- Radiological markers such as chest X-rays to reveal lung abnormalities characteristic of TB
- Blood tests to measure inflammatory markers like C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), which are elevated during active infection
- Lipoarabinomannan (LAM) antigen detection in urine, which is useful for diagnosing TB in HIV-positive patients, as noted in studies such as 1. These markers are essential because TB bacteria grow slowly, making diagnosis challenging, and they help clinicians determine if a patient has latent TB infection (which requires preventive therapy) or active TB disease (requiring full treatment regimens), as well as monitor treatment response over time, as discussed in guidelines like those found in 1 and 1.
From the Research
TB Markers
TB markers, also known as tuberculosis markers, are tests used to detect the presence of tuberculosis (TB) infection in an individual. These markers can be used to diagnose both active and latent TB infection.
Types of TB Markers
- Tuberculin Skin Test (TST): a traditional test that involves injecting a small amount of tuberculin into the skin to check for a reaction, indicating the presence of TB infection 2, 3, 4, 5, 6.
- Interferon-Gamma Release Assays (IGRAs): blood tests that measure the release of interferon-gamma in response to TB-specific antigens, including:
Characteristics of TB Markers
- Sensitivity and Specificity: IGRAs, such as T-SPOT.TB and QuantiFERON-TB Gold, have been shown to be more sensitive and specific than TST in certain populations, including HIV-infected individuals and those with immunosuppression 2, 3, 5.
- Advantages and Disadvantages: IGRAs have the advantage of not cross-reacting with Bacillus Calmette-Guérin (BCG) or most non-tuberculous mycobacteria, but may have higher costs and require specialized equipment 2, 6.
- Clinical Use: TB markers are used to diagnose latent TB infection, monitor treatment response, and screen high-risk populations, such as healthcare workers and individuals with HIV infection 3, 5.