Do results of the T-SPOT.TB interferon-γ release assay change after treatment of tuberculosis?

SummaryBackgroundInterferon-gamma (IFN-γ) production by lymphocytes exposed to antigens specific of Mycobacterium tuberculosis has been shown to correlate with antigen load and disease activity.Aim of studyTo determine whether treatment of tuberculosis (TB) led to a decrease and/or a reversion of results of a IFN-γ release assay (T-SPOT.TB, Oxford Immunotec, UK) and thus if T-SPOT.TB could be used to monitor response to treatment.MethodsQualitative and quantitative analysis (SFUs: spot-forming units) of T-SPOT.TB® in HIV-negative patients with TB, during initial 2 weeks of treatment (T0), at end of treatment (TE) and 6 months later (TE + 6).ResultsMean SFU (SD) was 75 (58; n = 62) at T0, 46 (55; n = 55) at TE, and 33 (46; n = 41) at TE + 6; positive rate was 98%, 93% and 98%, respectively. SFUs (paired samples, n = 36) decreased significantly between T0 and TE; 2 reversions occurred between T0 and TE (6%), but none between TE and TE + 6. Of 6 patients (17%) with an increase in SFUs between T0 and TE, 5 had a favourable outcome at TE and TE + 6.ConclusionDecrease in SFUs under treatment suggests a relationship with antigen load; however, persisting high SFUs were not predictive of unfavourable outcome and test reversion was rare.This trial was registered at www.clinicaltrials.gov (NCT00595907).