Within-Subject Variability and Boosting of T-Cell Interferon-γ Responses after Tuberculin Skin Testing

Abstract

When using a two-step screening strategy it appears safe to perform a QuantiFERON-TB-GIT or T-SPOT.TB IGRA within 3 days of performing the TST. A 3-spot or 80% IFN-gamma response variation, on either side of baseline values, explains 95% of the short-term variability and may be useful for interpreting conversions and reversions, and values close to the cut-point.