In face of the increased rates of tuberculosis in residents of long term care facilities, annual screening for latent tuberculosis is recommended. Tuberculin skin testing using purified protein derivative (PPD) is used for this purpose. Sensitivity of the PPD testing is, however, dependent on a normal T cell function. It is now evident that the immune system undergoes age-associated alteration known as immune senescence. The depressed T-cell responses may clinically manifest as attenuated delayed-type hypersensitivity. This attenuated reaction may affect the sensitivity of the PPD in detection of latent TB in the elderly.
This prospective study will examine the utility of interferon-gamma (IFN-γ) based assay, T-SPOT.TB, for detection of latent tuberculosis in nursing home patients who are 65 years of age or older.