High rates of indeterminate interferon-gamma release assays for the diagnosis of latent tuberculosis infection in liver transplantation candidates

Background and aims: Screening for latent tuberculosis infection (LTBI) is recommended prior to solid organ transplantation. Interferon-gamma release assays (IGRAs) are the most widely used test for LTBI screening; however, assessment of IGRA performance in patients with end-stage liver disease is limited. The purpose of this study was to evaluate the prevalence and predictors of indeterminate (INDT) IGRA results in liver transplantation candidates. 

Methods: Between March 2011 and May 2018, we retrospectively analyzed 155 patients undergoing liver transplantation assessment, who underwent IGRA testing (Quantiferon-TB Gold, QFT-G) to exclude LTBI. Characteristics of patients, including age, gender, etiology of liver disease, MELD score, and absolute lymphocyte counts, were compared by QFT-G result (determinate vs INDT). 

Results: Of the 155 patients screened, the rate of positive, negative, and INDT results were 5.2%, 69.8%, and 25%, respectively. The only variable independently associated with an indeterminate test on multivariate analysis was MELD score (odds ratio = 1.07, 95% CI = 1.01-1.14 per unit increase; P = 0.014). In 95% of INDT tests, both TB antigen tube and the positive control tube were negative and repeat testing gave the same indeterminate result, suggestive of anergy rather than laboratory error. 

Conclusions: Our study suggests a high rate of INDT IGRA results during screening of liver transplant candidates for LTBI, associated with severity of liver disease and anergy. Because of the high rate of INDT QFT-G testing in this setting, individualized risk assessment is required including a thorough assessment of clinical risk factors and knowledge of local TB prevalence.