Factors Associated with a Strong Response to the T-SPOT.TB in Patients with Extrapulmonary Tuberculosis.

Limited data are available on which factors are associated with strong immunologic responses to T-SPOT.TB. We investigated the factors associated with strong positive responses in patients with extrapulmonary tuberculosis (E-TB). Of 173 patients with E-TB who gave positive results on T-SPOT.TB, 26 (15%) with a strong positive response (defined as ≥1,000 spot-forming units (SFU)/2.5×10(5) PBMC to ESAT-6 or CFP-10) and 71 (41%) with a low positive response (≤ 99 SFU (6-99 SFU)/2.5×10(5) PBMC) were further analyzed. Miliary TB was independently associated with a strong positive response to T-SPOT.TB, while advanced age and immunosuppression were independently associated with weak positive T-SPOT.TB responses.