Borderline QuantiFERON results and the distinction between specific responses and test variability - 19/07/18
Abstract |
Background |
QuantiFERON (QFT) results near the cut-off are subject to debate. We aimed to investigate which borderline QFT results were due to Mycobacterium tuberculosis (Mtb)-specific responses or to test variability.
Methods |
In a contact investigation, tuberculin skin test (TST), QFT and T-SPOT.TB (T-SPOT) were performed in 785 BCG-unvaccinated contacts. Contacts with a low-negative (<0.15), borderline (0.15–0.35), low-positive (0.35–0.70) or high-positive QFT (≥0.70 IU/mL) were compared with respect to exposure, TST and T-SPOT results. Development of active tuberculosis was assessed.
Results |
Borderline QFT results occurred in threefold excess over test variability (p = 0.0027). In contacts with low-negative, borderline or positive QFT results, a positive TST occurred in 24.9%, 62.1% and 91.4% (p < 0.0001) and a positive T-SPOT result in 6.3%, 41.3% and 86.4%, respectively (p < 0.0001). Two-third (20/29) of contacts with a borderline and 14/16 (88%) with a low-positive QFT had a positive TST and/or T-SPOT, indicating probable Mtb-infection. During 12 years of follow-up, seven patients were diagnosed with active tuberculosis, two of whom after a low-positive QFT.
Conclusions |
In this study, most borderline and low-positive QFT results were Mtb-specific, showing the biological significance of a borderline QFT. The clinical relevance, however, will be most distinct in patients who are or will be immunocompromised.
Le texte complet de cet article est disponible en PDF.Keywords : Elispot, Interferon-gamma release tests, Cut-off, QuantiFERON, Tuberculosis
Plan
Vol 111
P. 102-108 - juillet 2018 Retour au numéro
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