Asymptomatic people who are at high risk of infection should be screened for tuberculosis (TB) through active case-finding.

1. Targeted screening programmes in high-risk populations (Prisons, homeless hostels or shelters, or substance misuse services; London or Birmingham).

2. People who have been in contact with a person with active pulmonary or laryngeal TB

3. People who are immunocompromised at high risk for latent TB infection

4. People starting specialist biologic drug treatment for inflammatory conditions with anti-tumour necrosis factor (TNF)-alpha agents such as infliximab, should be screened for active and latent TB.

5. For people who are new entrants to the UK from a high TB prevalence country

6. People who are new NHS employees

Specialist screening tests

To identify latent tuberculosis (TB) infection

Interpret taking into account the person's immune status, history of exposure to TB and the Bacillus Calmette-Guérin (BCG) vaccination, and other risk factors.

1. Mantoux test (tuberculin skin test)
   Tuberculin is injected intradermally.
   The skin is inspected for signs of a local skin reaction (induration) after 2–3 days
   The test is considered positive at an induration of 5 mm or more, regardless of previous BCG vaccination history.
   

2. Interferon gamma release assay (IGRA) test
   This is a blood test based on detecting the response of white blood cells to TB antigens.
   It is less likely to give false positive results compared with a Mantoux test and gives a rapid result.

Which populations can have which test?

• Mantoux test:
  children and young people aged 2–17 years who have been in close contact with people with pulmonary or laryngeal TB
  new entrants to the UK from high TB prevalence countries.

• Both a Mantoux test and IGRA: people who are severely immunocompromised at risk of TB.

• Single IGRA test: people younger than 65 years of age from under-served groups (such as the homeless or substance misusers)

Tests are positive for latent TB infection

1. The person should be assessed for active TB

2. Evaluate clinical symptoms and chest X-ray

3. Consider arranging three deep cough sputum samples, with preferably one early morning sample:
   test for Ziehl–Nielsen acid-fast bacilli
   culture for Mycobacteria culture
   and specialist molecular tests/drug sensitivity testing, depending on local laboratory protocols

4. The person should be treated for latent TB infection by the local multidisciplinary TB team to prevent progression to active disease.

Drug treatments for latent TB

1. Three months of isoniazid (with pyridoxine) and rifampicin, or

2. Six months of isoniazid (with pyridoxine).