Figure 1

Pre-treatment and post-treatment interferon-γ responses in nursing students treated with isoniazid preventive therapy for 6 months (N = 10). Baseline interferon-γ (IFN-γ) levels were measured using the QuantiFERON-TB Gold In Tube assay at the time of latent tuberculosis infection diagnosis (January/February 2004). The second measurement was made in January 2005, 4 months after isoniazid (INH) preventive therapy completion. The third measurement was made in July 2005, 10 months after INH treatment completion. All subjects were positive by the QuantiFERON-TB Gold In Tube assay and tuberculin skin test at baseline. The QuantiFERON-TB Gold diagnostic cut-point of 0.35 IU/mL is shown as a horizontal dotted line. IFN-γ levels >10.0 IU/mL have been shown as 10 IU/mL