Elevated Microbially-Derived Metabolites in Autism: A Possible Diagnostic Screening Test for a Distinct ASD Phenotype

Many studies have confirmed that a subset of children with autism spectrum disorder (ASD) have unusually high urinary concentrations of harmful microbially-derived metabolites (MDMs) such as p-cresol sulfate and indoxyl sulfate. We hypothesized that these MDMs may affect neurodevelopment through the gut-brain axis and that a sub-phenotype characterized by gut dysbiosis may be present in most ASD individuals. This multi-site study involved measuring the concentrations of many MDMs in the urine of 52 children with ASD and 47 healthy, typically developing (TD) children, aged 2 to 11 years. The measurements were conducted first with untargeted semiquantitative Liquid Chromatography and Mass Spectrometry (LC-MS), followed by targeted quantitative LC-MS. The ASD group had significantly higher concentrations of many MDMs compared to the TD group. The MDMs included phenylalanine-derived, tryptophan-derived, and yeast-derived MDMs. Almost all children with ASD had one or more MDMs at concentrations above any TD child, and sometimes 100-1000x higher. The children with ASD had an average of 3 MDMs at levels above any TD child, compared to zero (by definition) for the TD children. Classification using one or more elevated MDM yielded a sensitivity of 90% and a specificity of 100%. This MDM System^™ is a promising non-invasive method for diagnostic screening for ASD in children ages 2 to 11 years. These data also suggest approximately 90% of children with ASD have a distinct phenotype of ASD, which we propose naming ASD associated with Microbially-Derived Metabolites (ASD-MDM), defined by quantitative laboratory measurements of these metabolites in urine.