What test is used to test TB infection in RA management?

• A. Chest x-ray
• B. IGRA
• C. TB skin test
• D. Sputum culture

Answer: (B)

Screening for latent TB infection before starting RA therapies that suppress the immune system is essential because treatment can reactivate TB. The test that best detects TB infection in this context is the Interferon-Gamma Release Assay. It measures immune response to TB-specific antigens and, unlike the TB skin test, is not affected by prior BCG vaccination, giving higher specificity. It also usually requires only one visit, which makes it a convenient choice in busy clinics.

Chest x-ray can help assess for active disease but does not identify latent infection. Sputum culture detects active TB but not latent infection. The TB skin test can yield false positives in BCG-vaccinated individuals and false negatives in those with immune suppression, making IGRA the preferred option for latent TB screening in RA management. A positive IGRA warrants evaluation for active TB before initiating therapy.