Interferon gamma release assays (IGRA) have been shown to be more specific and sensitive for the detection of tuberculosis (latent or active infection) than the tuberculin skin test (TST) in immunocompetent individuals. However, very little data are available concerning the relative performance of IGRA and TST in immunosuppressed individuals from other causes than HIV.

The investigators hypothesize that IGRAs would be more sensitive and specific than the TST in a group of renal transplant recipients under chronic immunosuppressive treatment for detecting latent tuberculosis infection.

In a recent study (Triverio PA et al. "Interferon-gamma release assays versus tuberculin skin testing for detection of latent tuberculosis in haemodialysis patients". Nephrol Dial Transplant 2009; 24: 1952-6), the investigators had compared 2 IGRAs (T-SPOT.TB and Quantiferon Gold) with the TST and shown that one IGRA was clearly more sensitive than the TST but that both tests had a very low sensitivity for detecting prior TB.

This study applies the same protocol to renal transplant recipients undergoing routine annual check-up visits: questionnaire with detailed collection of risk factors for latent tuberculosis infection (LTBI), history of prior contact with tuberculosis (TB), BCG (Bacille of Calmette and Guerin vaccine), prior TB or LTBI, treatment for TB or LTBI, analysis of chest X-ray for signs of prior TB, on-going treatment, level of immunosuppression (CD4 lymphocytes), simultaneous blood sampling for T-SPOT.TB and Quantiferon Gold, and tuberculin skin testing.

Inclusion Criteria:

• prior renal transplantation;
• age > 18;
• stable clinical condition

Exclusion Criteria:

• hypersensitivity to tuberculin skin testing

Patients followed by the Division of Nephrology after renal transplantation, and undergoing routine annual check-ups, in stable clinical condition, aged above 18