Tuberculosis after a borderline QuantiFERON result during screening before infliximab

Extract

Patients who are eligible for treatment with immunosuppressive drugs such as antagonists of tumour necrosis factor (TNF)-α must be screened for latent tuberculosis infection (LTBI), as stated in the recent European standards for tuberculosis (TB) care [1]. Although there are controversies regarding optimal screening [2], interferon-γ release assays such as QuantiFERON-TB Gold (QFT) (Qiagen, Hilden, Germany) are nowadays frequently used. The formal cut-off for a positive QFT is ≥0.35 IU·mL⁻¹ interferon-γ. However, a recent study published in the European Respiratory Journal found that a significant proportion of results just below this cut-off, so called borderline results, represented true infection with Mycobacterium tuberculosis [3]. We present a patient who clearly illustrates the clinical significance of borderline QFT results in patients screened before immunosuppression.