Measurement of urine indolylacroylglycine is not useful in the diagnosis or dietary management of autism.
Urine IAG testing gives no useful information for diagnosing autism or planning diets.
01Research in Context
What this study did
The team collected morning urine from the children. Thirty had autism, thirty had other special needs, and thirty were typically developing.
They measured levels of a molecule called indolylacroylglycine (IAG). Parents also filled out diet logs and GI-symptom checklists.
What they found
IAG levels were the same across all three groups. Regression history, stomach pain, or diet changes made no difference.
In short, urine IAG cannot tell you which child has autism.
How this fits with other research
Boswell et al. (2023) pooled 25 similar studies and reached the same blank result for all tryptophan-breakdown products, including IAG. Their bigger head-count confirms this paper’s “no signal” verdict.
Lussu et al. (2017) looked at the same kind of urine samples the same year but used a wider metabolomics net. They did spot some different patterns, yet when both studies zeroed in on IAG they agreed: it does not separate ASD from controls. The apparent contradiction melts away once you see one lab hunted for a single target while the other scanned hundreds.
Wang et al. (2010) tried creatine in urine as a screener and also struck out. The pattern is clear: single urine metabolites keep failing as autism flags.
Why it matters
Stop sending urine packets to labs that promise “autism metabolite screens.” The data say you will get noise, not answers. Spend your assessment hours on validated tools like the ADOS and on interviews that guide real intervention.
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02At a glance
03Original abstract
To measure urine indolylacroylglycine (IAG) excretion using the IAG:creatinine ratio in children with autism spectrum disorder (ASD) compared with two groups of age matched controls, one with special needs but without ASD (SEN) and one typically developing (TD) and in subgroups with/without current gastrointestinal problems and ASD with and without regression. IAG:creatinine ratio was measured in the urine of 279 children aged 10-14 years: 129 children with ASD (28 with and 101 without regression), 62 SEN controls and 88 TD controls. The prevalence of gastro-intestinal symptoms (GIS) was recorded. No differences were found in the urine IAG:creatinine ratio among groups ASD, TD and SEN; nor in the ASD groups with/without regression, nor in those with/without GIS. This study finds no evidence of increased urine IAG excretion in children with ASD, with or without GIS or with or without regression. Urinary IAG measurements in children with ASD offer no support for increased presence of neuroactive peptides proposed to result from increased gut permeability. We found measurement of urinary IAG to have no value in the diagnosis of autism or in the dietary management of children with ASD. Autism Res 2017, 10: 408-413. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.
Autism research : official journal of the International Society for Autism Research, 2017 · doi:10.1002/aur.1688