Tuberculosis (TB) contact tracing is a massive part of public health in the UK, especially for the UKMLA AKT. The goal is to catch active cases early and identify those with Latent TB Infection (LTBI) before it reactivates.

In the UK, we follow the NICE guidelines, which use a specific "concentric circle" approach—starting with the closest contacts (household) and expanding only if needed.

1. Screening Protocol

The screening process depends on the contact's age and their BCG vaccination status. We primarily use two tests:

• Mantoux Test (Tuberculin Skin Test): The first-line screening tool.
• Interferon-Gamma Release Assay (IGRA): Used if the Mantoux is positive or if the person has had a BCG vaccine (to avoid false positives).

2. Latent TB Treatment

If a patient has a positive IGRA but a normal chest X-ray (no active disease), they have Latent TB. We treat this to prevent future reactivation.

Standard LTBI Regimens:

1. 3 months of Isoniazid and Rifampicin (with Pyridoxine/Vit B6) — The "3RH" regimen
2. 6 months of Isoniazid (with Pyridoxine) — The "6H" regimen

3. BCG Vaccination

The BCG is a live-attenuated vaccine. In the UK, we don't do universal school vaccination anymore; it's targeted.

• Who gets it? Neonates in high-incidence areas (TB rate >40/100,000) or those with a parent/grandparent from a high-incidence country.
• The Rule: You must perform a Mantoux test before giving the BCG to anyone over 6 years old (or infants over 3 months with a history of travel/contact) to ensure they aren't already infected.

Let me pull up some high-yield lessons and a flowchart to help you visualize the screening algorithm!

The flowchart above gives you a clear path for how we handle contacts in a clinical setting.

A few high-yield "exam traps" to watch out for:

• The BCG Effect: If a patient has had a BCG vaccine, their Mantoux test might be positive even if they don't have TB. That’s why we must do an IGRA to confirm. IGRA is specific to M. tuberculosis and isn't affected by the BCG strain.
• Window Period: If a contact is tested too early (less than 6 weeks after exposure), the tests might be negative. We often repeat the test at 6 weeks if the initial one was negative.
• HIV/Immunosuppression: In these patients, the Mantoux test is less reliable because they can't mount a skin response (anergy). We lean much more heavily on IGRA and clinical suspicion here.
• Treatment Side Effects:
  • Rifampicin: Orange secretions (tears/urine) and enzyme induction (watch out for the COCP!).
  • Isoniazid: Peripheral neuropathy (always co-prescribe Pyridoxine/Vit B6) and hepatotoxicity.

Would you like to try a few practice questions on this to see how it's tested in the AKT?