Equal sensitivity of the new generation QuantiFERON-TB Gold plus in direct comparison with the presious test version QuantiFERON-TB Gold IT
23 February 2017 (online)
QuantiFERON-TB Gold IT analysis interferon-gamma release from CD4+ T-cells after stimulation with specific tuberculosis (TB) antigens. Its sensitivity is approximately 80% for active TB. A new test generation (QFTGplus) also analysis the response of CD8+ T-cells. The manufacturer advertises with increased sensitivity. We investigated both test generations in a direct head-to-head comparison in a German pulmonary hospital. 163 persons (35.6%), including 77 (47.2%) HCW and 86 (52.8%) TB-suspects, gave their signed consent to the study. Twenty four (27.9%) and thirty three (38.4%) TB-suspects had final diagnoses of aTB with and without bacteriological confirmation, respectively, were enroled. Twenty nine suspects (29/86; 33.7%) had no active TB, but ten (10/86; 11.6%) of them had post-specific anomalies in chest x-ray. Four TB-subjects (4/86; 4.7%) were immunocompromised. Only QFTG-IT gave invalid results in two cases (1.2%). Positivity rates (89.5%; 95%-CI 0.81 – 0.97) of both tests were identical for TB patients, irrespective of whether diagnosis was only clinically established (28/33; 84.8%; 95%-CI 0.71 – 0.98) or bacteriologically confirmed (23/24; 95.8%; 95%-CI 0.88 – 1.04). Positivity rates of the QFTGplus were statistically indifferent for TB suspects with post-specific changes in chest x-ray (5/10 versus 6/10; p = 1.0) and for HCW (10/77 versus 8/77; p = 0.8). Of the four immuno-compromised suspects, both tests generated positive results for the patient with and negative results for the subjects without aTB. IFG concentrations were higher in the QFTG-IT than in the QFTGplus test tubes. In summary, sensitivity rates for active TB were identical and the maufacterer's promises of higher sensitivity of the new test generation could not be confirmed in our study setting.