Improved sensitivity of an interferon-gamma release assay (T-SPOT.TB™) in combination with tuberculin skin test for the diagnosis of latent tuberculosis in the presence of HIV co-Infection
1 Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, Basel, Switzerland
2 Institute of Medical Microbiology, University of Basel, Basel, Switzerland
3 University Clinic for Infectious Diseases, University Hospital Bern and University of Bern, Bern, Switzerland
4 Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, Zurich, Switzerland
5 Division of Infectious Diseases, University Hospital Lausanne, Lausanne, Switzerland
6 Division of Infectious Diseases, University Hospital Geneva, Geneva, Switzerland
7 Cantonal Hospital, St. Gallen, Switzerland
8 Regional Hospital, Lugano, Switzerland
9 Cantonal Hospital, Olten, Switzerland
BMC Infectious Diseases 2011, 11:319 doi:10.1186/1471-2334-11-319Published: 15 November 2011
Interferon-gamma release assays (IGRA) are more specific than the tuberculin skin test (TST) for the diagnosis of Mycobacterium tuberculosis infection. Data on sensitivity are controversial in HIV infection.
IGRA (T-SPOT.TB) was performed using lymphocytes stored within 6 months before culture-confirmed tuberculosis was diagnosed in HIV-infected individuals in the Swiss HIV Cohort Study.
64 individuals (69% males, 45% of non-white ethnicity, median age 35 years (interquartile range [IQR] 31-42), 28% with prior AIDS) were analysed. Median CD4 cell count was 223 cells/μl (IQR 103-339), HIV-RNA was 4.7 log10 copies/mL (IQR 4.3-5.2). T-SPOT.TB resulted positive in 25 patients (39%), negative in 18 (28%) and indeterminate in 21 (33%), corresponding to a sensitivity of 39% (95% CI 27-51%) if all test results were considered, and 58% (95% CI 43-74%) if indeterminate results were excluded. Sensitivity of IGRA was independent of CD4 cell count (p = 0.698). Among 44 individuals with available TST, 22 (50%) had a positive TST. Agreement between TST and IGRA was 57% (kappa = 0.14, p = 0.177), and in 34% (10/29) both tests were positive. Combining TST and IGRA (at least one test positive) resulted in an improved sensitivity of 67% (95% CI 52-81%). In multivariate analysis, older age was associated with negative results of TST and T-SPOT.TB (OR 3.07, 95% CI 1,22-7.74, p = 0.017, per 10 years older).
T-SPOT.TB and TST have similar sensitivity to detect latent TB in HIV-infected individuals. Combining TST and IGRA may help clinicians to better select HIV-infected individuals with latent tuberculosis who qualify for preventive treatment.