Risk Assessment of Tuberculosis in Immunocompromised Patients. A TBNET Study

Rationale: In the absence of active tuberculosis, a positive tuberculin skin test (TST) or interferon-gamma release assay (IGRA) result defines latent infection with Mycobacterium tuberculosis, although test results may vary depending on immunodeficiency. Objectives: This study compared the performance of TST and IGRAs in five different groups of immunocompromised patients, and evaluated their ability to identify those at risk for development of tuberculosis. Methods: Immunocompromised patients with HIV infection, chronic renal failure, rheumatoid arthritis, solid-organ or stem-cell transplantation, and healthy control subjects were evaluated head-to-head by the TST, QuantiFERON-TB-Gold in-tube test (ELISA), and T-SPOT. TB test (enzyme-linked immunospot) at 17 centers in 11 European countries. Development of tuberculosis was assessed during follow-up. Measurements and Main Results: Frequencies of positive test results varied from 8.7 to 15.9% in HIV infection (n = 768), 25.3 to 30.6% in chronic renal failure (n = 270), 25.0% to 37.2% in rheumatoid arthritis (n = 199), 9.0 to 20.0% in solid-organ transplant recipients (n = 197), 0% to 5.8% in stem-cell transplant recipients (n = 103), and 11.2 to 15.2% in immunocompetent control subjects (n = 211). Eleven patients (10 with HIV infection and one solid-organ transplant recipient) developed tuberculosis during a median follow-up of 1.8 (interquartile range, 0.2-3.0) years. Six of the 11 patients had a negative or indeterminate test result in all three tests at the time of screening. Tuberculosis incidence was generally low, but higher in HIV-infected individuals with a positive TST (3.25 cases per 100 person-years) than with a positive ELISA (1.31 cases per 100 person-years) or enzyme-linked immunospot result (1.78 cases per 100 person-years). No cases of tuberculosis occurred in patients who received preventive chemotherapy. Conclusions: Among immunocompromised patients evaluated in this study, progression toward tuberculosis was highest in HIV-infected individuals and was poorly predicted by TST or IGRAs.