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

A Comparison of Traditional Tuberculosis Screening Methods With the T-SPOT TB Test for the Diagnosis of Latent Tuberculosis Infection 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.

Inclusion Criteria:

Inclusion criteria for the study are broad.

• Participants can be enrolled regardless of race, gender, risk of exposure to TB, metabolic disorders or coinfection with non-TB agents.

• Only participants who have provided written informed consent will be included.

• Patients belonging to the four following groups will be considered eligible for tuberculosis screening and inclusion in the T-SPOT ELISPOT study:

  • Patients with end stage renal disease receiving hemodialysis or peritoneal dialysis;
  • Recipients of solid organ transplants;
  • Recipients of, or candidates for, an allogeneic stem cell transplant for hematologic malignancies;
  • Patients with rheumatologic diseases (e.g., systemic lupus erythematosus [SLE], rheumatoid arthritis, psoriasis) who are receiving, or about to receive, immunosuppressive therapy, including corticosteroids and anti-TNF alpha inhibitors.

Exclusion Criteria:

• Individuals who have not signed an informed consent
• Hemophiliacs or individuals who, on the advice of the enrolling physician, may otherwise be at increased risk of an adverse reaction to venipuncture or tuberculin skin test administration