A novel application of the interferon-gamma release assay (IGRA) among end-stage heart failure patients awaiting heart transplantation.

Background: Interferon-gamma release assays (IGRAs) measure immune responses to pathogen-specific antigens such as tuberculosis. However, the assay hinges on a functional immune system. Whether IGRAs can be used to identify heart transplant candidates with impaired immunity and worse prognosis is not known.

Methods: From August 1st^, 2014 to August 31st^, 2018, all heart transplant candidates at a medical center in Taiwan who received an IGRA (QuantiFERON®-TB Gold In-Tube) during transplant evaluation to screen for latent tuberculosis infection were included. Inadequate immunity was defined as a response of <1 IU/ml of interferon-γ (IFN-γ) to the common mitogen in the positive control tube of the IGRA. Patients were followed until death or January 31st, 2019 for all-cause mortality and subsequent infections.

Results: A total of 103 patients were included, and 23 (22.3 %) had inadequate mitogen responses. After a median follow-up duration of 676 days (interquartile range [IQR] 387-1299), 34 (33.0 %) patients received a heart transplant and 23 (22.3 %) patients died. Forty-eight (46.6 %) patients developed infections, predominantly bacteremia (37.5 %). Those with inadequate mitogen responses had significantly higher rates of mortality (39.1 % vs. 17.5 %, p = 0.028) and infections (65.2 % vs. 41.3 %, p = 0.042). In the multivariate analysis, inadequate responses to mitogen were significantly associated with mortality and infections (hazard ratio [HR] 3.36, confidence interval [CI] 1.22-9.23, p = 0.019; HR 2.75, CI 1.18-6.40, p = 0.019).

Conclusions: Patients with heart failure and inadequate mitogen responses by IGRAs had a higher risk of mortality and infection. IGRAs may have a novel application in prognostication of heart transplant candidates.