Tuberculosis (TB) Screening for the Diagnosis of Latent TB in Immunocompromised Populations

The tuberculin skin test (TST) has been the gold standard for diagnosing latent tuberculosis for almost 100 years. While this test performs reasonably well in healthy, non-bacille Calmette-Guerin (BCG) vaccinated populations, it is believed to perform less well in patients who do not have intact cellular immune systems (immunocompromised).

The investigators hypothesize that a new test, the T-SPOT TB ELISPOT test will provide a more accurate measurement of latent infection in immunocompromised people. This study will compare the TST to the T-SPOT TB ELISPOT test, and to the results of an expert physician diagnostic panel.

Main Study Question:

We propose to investigate the correlation between the traditional TST-based method of screening for latent tuberculosis infection in specific immunocompromised populations as recommended by Canadian and American standards: the T-SPOT TB ELISPOT test: and an expert tuberculosis physician panel incorporating the Mantoux test, a risk factor survey, and a chest radiograph.

Secondary Study Question:

In a subset of patients who have tested positive on both the Mantoux and T-SPOT ELISPOT tests prior to undergoing additional immune suppression i.e., patients pre-bone marrow transplant and rheumatology patients pre-receipt of anti-TNF alpha therapy or high dose corticosteroids, we propose to repeat the T-SPOT ELISPOT and Mantoux after immune suppression to assess the development of cutaneous anergy.