Breath analysis in gastrointestinal graft-versus-host disease after allogeneic hematopoietic cell transplantation

Volatile organic compounds (VOCs) are generated during pathologic processes, and their assessment can be used to diagnose and monitor a variety of diseases. Given the role of the microbiome in graft-versus-host disease (GVHD), we hypothesized that microorganisms producing volatile metabolites may alter VOCs expelled in breath in patients with gastrointestinal (GI) GVHD. In this pilot study, exhaled breath samples were obtained from 19 patients with grade 2 to 4 acute GI GVHD, 10 patients with no GVHD at day 100, and 10 healthy control subjects; the samples were analyzed by using mass spectrometry. Overall, nine (47%) patients had grade 2 GVHD, eight (42%) patients had grade 3 GVHD, and two (11%) patients had grade 4 GVHD; 26% had upper GI, 21% had lower GI, and 53% had both upper and lower GI manifestations. Stepwise canonical discriminant analysis identified 5 VOCs distinguishing patients with and without GI GVHD: 2-propanol, acetaldehyde, dimethyl sulfide, isoprene, and 1-decene (Wilks' Λ, 0.43; F statistic, 6.08; P = .001). The model correctly classified 89% (17 of 19) and 90% (9 of 10) of patients with and without GI GVHD, respectively. Breath analysis is a feasible and promising noninvasive method to detect acute GI GVHD. Further study of serial breath analysis and the gut microbiome in a larger cohort are ongoing to validate these findings.