Screening for Latent Tuberculosis Infection Recommended

Tuberculosis remains an important preventable disease, including active tuberculosis infection, which may be infectious and latent infection (LTBI), which is asymptomatic and not infectious, but can later reactivate and progress to active disease.

People who are considered at increased risk include people who were born in or have lived in countries where tuberculosis is highly prevalent, or who have lived in group settings where exposure to tuberculosis is more likely, such as homeless shelters or correctional facilities.

The US Preventive Services Task Force (USPSTF, Rockville, MD, USA) recommends screening for latent tuberculosis infection in populations at increased risk. The USPSTF reviewed the evidence on screening for LTBI in asymptomatic adults seen in primary care, including evidence dating from the inception of searched databases. This is a B recommendation, indicating that there is high certainty that the net benefit is moderate, or there is moderate certainty that the net benefit is moderate to substantial.

The USPSTF found adequate evidence that accurate screening tests are available to detect LTBI. Screening tests include the Mantoux tuberculin skin test (TST) and interferon-gamma release assays (IGRAs); both are moderately sensitive and highly specific. The TST requires intradermal placement of purified protein derivative and interpretation of response 48 to 72 hours later. The skin test reaction is measured in millimeters of the induration (a palpable, raised, hardened area or swelling). Interferon-gamma release assays require a single venous blood sample and laboratory processing within eight to 30 hours after collection. Two types of IGRAs are currently approved by the US Food and Drug Administration: T-SPOT.TB (Oxford Immunotec Global, Abingdon, UK) and QuantiFERON-TB Gold In-Tube (Qiagen, Hilden, Germany).

When using a positive threshold of 10 mm of induration, the TST has moderate sensitivity and high specificity for detection of LTBI. Based on pooled analyses of studies reviewed by the USPSTF, when using a positive threshold of 10 mm, the TST has sensitivity of 79% (11 studies; n = 988) and specificity of 97% (nine studies; n = 9,651). Pooled analyses of the T-SPOT.TB test (a type of IGRA) indicate sensitivity of 90% (16 studies; n = 984) and specificity of 95% (5 studies; n = 1,810). Pooled analyses of the QuantiFERON-TB Gold In-Tube test (another type of IGRA) indicate sensitivity of 80% (24 studies; n = 2,321) and specificity of 97% (4 studies; n = 2,053).

The USPSTF found adequate evidence that accurate screening tests for LTBI are available, treatment of LTBI provides a moderate health benefit in preventing progression to active disease, and the harms of screening and treatment are small. The USPSTF has moderate certainty that screening for LTBI in persons at increased risk for infection provides a moderate net benefit. The study was published on September 6, 2016, in The Journal of the American Medical Association.

Related Links:
US Preventive Services Task Force
Oxford Immunotec
Qiagen