Tuberculosis skin test, but not interferon-γ-releasing assays is affected by BCG vaccination in HIV patients.

Objective: Of this study was to compare the results of tuberculin skin test (TST) with two interferon-γ releasing-assays (IGRA) in a cohort of HIV positive patients, to analyze impact of prior Bacille-Calmette-Guérin (BCG)-vaccination.

Methods: Prospective cross sectional study, enrolling only asymptomatic adult HIV infected outpatients from a large German University hospital clinic. All participants were simultaneously tested for latent tuberculosis infection (LTBI) by QuantiFERON-TB Gold, T-SPOT.TB and TST. Only individuals with available definite results (positive/negative, indeterminates excluded) from all three test systems and recalling BCG-vaccination status by interview questionnaire were evaluated.

Results: From 286 study participants, 133 were evaluable; BCG-vaccination history was positive for 18 individuals, and negative for 115. The proportion of individuals with a positive TST was significantly higher for vaccinated (n = 6, 33.3%) than for unvaccinated individuals (n = 13, 11.3%, p = 0.013). There were no significant differences in the proportion of patients with CDC stage C, origin from a TB endemic country or in the CD4 count between the two groups.

Conclusion: TST but not IGRAs interfered significantly with prior BCG vaccination in a cohort of HIV infected individuals from a low prevalence TB country. Therefore IGRA should preferentially be used for LTBI-testing in BCG-vaccinated adult HIV-patients.