Urine Test for Autism: How a New Study Could Help Diagnose Children

Autism prevalence has climbed steadily for two decades. The most recent surveillance data from the CDC’s Autism and Developmental Disabilities Monitoring Network estimates that roughly 1 in 31 children in the United States has autism, up from 1 in 36 just two years earlier. Across CDC monitoring sites, autism identification has risen roughly 10% to 20% every two years, with the steepest increases now seen among girls and several racial and ethnic minority groups.

Diagnosis itself has not kept pace. Reliable identification is possible by 18 to 24 months of age, but the average age at which a child in the United States receives a formal autism diagnosis is nearly four years. The gap between a parent’s first concerns and a confirmed answer often stretches two to three years.

That delay matters because early intervention tends to be most effective when it begins prior to the age of 2, during the years of greatest brain plasticity. Getting both the accuracy and the timing right has become the central challenge for clinicians.

There is no blood test, brain scan, or single biomarker that confirms autism on its own. Currently, thorough autism testing and evaluation typically pulls together developmental history, direct observation, parent interviews, and input from teachers across multiple visits, which could take months.

The criteria come from the DSM-5-TR, which defines autism spectrum disorder through two core domains: persistent deficits in social communication and interaction and restricted, repetitive patterns of behavior or interests. Clinicians look across the full range of symptoms and signs of autism, including communication patterns, repetitive behaviors, sensory sensitivities, and related characteristics, when piecing a diagnosis together.

There are several types of autism tests in common use. The Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) is widely considered the gold standard for direct observation. A trained examiner uses age-appropriate modules to evaluate communication, social interaction, and play, with sessions typically running 30 to 60 minutes. The Autism Diagnostic Interview-Revised (ADI-R) gathers a detailed developmental history from parents or caregivers and can take 90 to 150 minutes. Additional tools include the Childhood Autism Rating Scale (CARS-2), the Autism Spectrum Rating Scales (ASRS), Social Responsiveness Scale (SRS-2), and screening instruments like the Modified Checklist for Autism in Toddlers (M-CHAT) used in primary care settings.

A complete autism evaluation combines several tools within the clinician’s own judgment, observations across settings, and input from teachers or other caregivers. That layered approach is what makes the process thorough, but also what makes it slow.

A study published in the journal Molecular Psychiatry by Arizona State University researchers and collaborators from Harvard Medical School, Rensselaer Polytechnic Institute, and clinical centers in Tennessee and Texas tested a different approach. Instead of observing behavior, the team analyzed urine samples for 17 microbial metabolites, the small molecules produced by bacteria in the gut, in children ages 2 to 11.

The reasoning behind the test connects two lines of research. First, a growing body of evidence suggests that many children with autism show altered gut microbiomes, with elevated levels of specific bacterial byproducts. Second, some of those metabolites are chemically related to neurotransmitters like serotonin and dopamine that influence mood, attention, and communication.

The researchers developed what they call the Microbially-Derived Metabolite System, or MDM System, which scores how many of those 17 metabolites exceed typical ranges in a child’s urine.

The research published in Molecular Psychiatry measured metabolite concentrations in 52 children diagnosed with ASD and 47 typically developing children, ages 2 to 11, recruited from four sites across the United States.

The differences were significant. Nearly all children with autism had at least one metabolite level exceeding the highest observed in the typically developing group. On average, children with autism had about three elevated metabolites, while children without autism had none. Some individual metabolite levels measured 100 to 1,000 times higher in the autism group.

In trials, the test correctly identified children with autism in the study sample with about 90% accuracy and did not misidentify any of the typically developing children. The elevated metabolites came primarily from amino acids involved in neurotransmitter pathways, including phenylalanine, tryptophan, and tyrosine, along with compounds connected to yeast and fungal activity in the gut.

The findings are consistent with more than 40 prior studies that have reported higher concentrations of gut-derived metabolites in children with autism.

The researchers describe the test as a screening tool, not a replacement for clinical evaluation. The MDM System identified roughly 90% of the autism cases in the study, which the team has proposed represents a possible autism subtype they call ASD-MDM, for autism associated with microbially-derived metabolites.

The study has limits. A sample of 99 children is small, and the researchers note that larger and more diverse trials are needed to validate the findings across different populations. Furthermore, the study’s sample of children age 2 to 11 does not get at the suggested targeted age of diagnosis, which is prior to the age of 4, and ideally prior to the age of 2. The metabolites represent associations, not causes; the study does not establish whether the gut microbiome contributes to autism or whether autism alters the gut microbiome.

For now, autism diagnosis still depends on the behavioral and developmental assessments outlined above. The new research adds to a wider body of work examining biological markers in autism, including imaging, genetic, and metabolic studies. Whether urine-based screening eventually fits into routine evaluation will depend on additional validation work.

For families navigating questions about a child’s development, comprehensive autism evaluation and ongoing autism treatment, including therapy and care coordination, are available through LifeStance providers across the country.