Utility of an immune cell function assay to differentiate rejection from infectious enteritis in pediatric intestinal transplant recipients

The Cylex Immune Cell Function Assay measures cell‐mediated immunity based on ATP production by stimulated CD4 + cells. We hypothesized that this test would discriminate acute cellular rejection (ACR) from infectious enteritis (IE) in pediatric intestinal transplant (ITx) recipients with allograft dysfunction. We retrospectively analyzed 224 Cylex assays drawn in 47 children who received 53 ITx. Samples were classified as stable, ACR, or IE based on clinical status. ATP values were analyzed using Kruskal–Wallis and t‐tests. Overall, there was a statistically significant difference in ATP values based on clinical status (p = 0.03); however, overlap was observed between groups. The median ATP value during ACR was significantly greater than during stable periods (p = 0.02). No difference was seen in IE vs. stability (p = 0.8). The difference in median ATP value in ACR vs. IE approached significance (p = 0.1). Relative to previous levels, ACR episodes were associated with a median ATP increase of 101 ng/mL and IE episodes with a decrease of 3 ng/mL (p = 0.3). These data indicate that the Cylex assay has limited utility in differentiating ACR from IE, largely due to interpatient variability. Following longitudinal intrapatient trends may be an adjunctive tool in discriminating IE from ACR and guiding immunosuppression adjustments in select patients.