Abstract
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Objectives To evaluate FDG PET as a non invasive technique to assess patients with clinically suspected acute graft versus host disease (GVHD) of the gastrointestinal tract (GIT) following Allogeneic Haemopoietic Stem Cell Transplantation (AlloHSCT).
Methods 20 AlloHSCT patients with clinically suspected acute GVHD of the GIT underwent FDG PET scanning prior to gastroscopy and colonoscopy within 7 days (mean 2.8 days). Biopsies of 4 upper and 4 lower GIT segments were obtained for histology, with 2 biopsies obtained per segment if normal macroscopically and on PET and 4 biopsies if abnormal macroscopically or on PET. The degree of PET GIT uptake in each bowel segment was graded 1-4 relative to the mediastinum, with patients considered positive for acute GVHD if >3 of 8 bowel segments had grade 3/4 FDG uptake.
Results 6/20 (30%) patients had biopsy proven acute GIT GVHD. PET was positive in 4/6 of these patients (Sensitivity 67%). Of the 14/20 biopsy negative patients, PET was falsely positive in 3 patients (Specificity 79%), with 1 of these patients subsequently confirmed as having Norovirus GIT infection. Positive predictive value of PET for acute GVHD was 57% and negative predictive value (NPV) 84%. Of 156 bowel segments evaluated, PET was concordant with endoscopic macroscopic findings in 124/156 (79%) and biopsy in 114/152 (75%) GIT segments. Overall, PET was correct in determining acute GIT GVHD status in 15/20 (75%) of patients.
Conclusions FDG PET demonstrates potential as a non invasive technique to evaluate suspected acute GIT GVHD. Its high NPV suggests it may be a useful technique to exclude GVHD however when positive further invasive biopsy to determine aetiology of active bowel inflammation is still required