Favourable survival in "Discordant" acute gastrointestinal graft versus host disease (GI-GVHD) is explained by mild clinical course and treatment-responsive disease.

We have previously reported that haematopoietic progenitor cell transplantation recipients with biopsy-negative acute Gastrointestinal Graft versus Host Disease (Discordant GVHD) demonstrate superior survival compared to "True Positive" cases. We aimed to elucidate this discrepancy by examining clinical and laboratory predictors of survival among patients treated for True Positive or Discordant GVHD. Data were obtained by retrospective chart review. At diagnosis, the incidence of severe symptoms, hypoalbuminaemia, hyperbilirubinaemia, and poor performance status were recorded. Following treatment, the incidence of non-response to first-line corticosteroids was assessed. Differences between cohorts were compared using Fisher's exact test. 74 patients were identified, comprising 55 (74%) True Positive and 19 (26%) Discordant GVHD cases. True Positive cases were significantly more likely to have baseline severe symptoms (84% vs. 36%; p = 0.0002) and hypoalbuminaemia (94% vs. 75%; p = 0.023). There was no significant difference between cohorts in terms of hyperbilirubinaemia or performance status. Non-response to corticosteroid therapy was observed significantly more frequently in the True Positive cohort (55% vs. 11%; p = 0.001). In summary, the superior survival observed in Discordant GVHD is explained by a less severe GI-GVHD phenotype at diagnosis and a greater likelihood of response to corticosteroids. Further research is warranted to explain biological mechanisms for these findings.