Differences in microbial metabolites in urine headspace of subjects with Immune Thrombocytopenia (ITP) detected by volatile organic compound (VOC) analysis and metabolomics

• Clear metabolic differences in headspace of urine between groups when analysed with SIFT-MS and multivariate statistical analysis.
• SIFT-MS offers a real-time, non-invasive method of analysing human samples.
• Changing the diet of those with ITP who suspect food intolerance did not lead to an increase in their platelet count.
• A number of specific VOCs could be identified as significantly different between ITP volunteers and healthy volunteers.
• Analysis of the whole metabolome looks more effective than isolating and identifying individual biomarkers.

ITP is an organ-specific autoimmune disorder characterised by a low platelet count whose cause is uncertain. A possible factor is food intolerance, although much of the information linking this with ITP is anecdotal. The role of food intolerance in ITP was studied by replacing a normal diet with an elemental diet (E028), but this did not increase platelet counts. Clear differences, however, were apparent between the volatile organic compounds (VOCs) in the urine headspace of patients with ITP and those present in healthy volunteers, which leads to speculation that abnormal metabolic activity of the intestinal microbiome may be a factor causing ITP. However, further work is needed to confirm this. There were also differences between the VOCs of patients on a normal diet and those on the elemental diet, and in this case, the VOCs involved are very likely to be of bacterial origin, as their production is affected by dietary manipulation. Many of these VOCs are known to be toxic.