Gut and Metabolic Biomarkers in Autism Spectrum Disorder: A Systematic Review of Body Fluid Signatures for Early Detection.

Baker et al. (2025) pooled every paper they could find on gut and metabolic markers for autism. They hunted for body-fluid tests that might spot ASD before classic signs show up.

The team screened thousands of records, kept the ones that compared children with ASD to typically developing peers, and graded the proof of each marker.

The review says the markers look exciting but still flimsy. Some kids with ASD do show odd amino-acid levels, unusual gut bugs, or urinary porphyrins, yet none of the tests are ready for the clinic.

Bottom line: the science is early-stage. Long-term studies that follow babies from birth are missing.

Cai et al. (2025) and Eggleston et al. (2018) both found high accuracy for microbe tests in stool or saliva. Baker et al. (2025) welcome these numbers but warn they rest on small, one-time snapshots.

Vargason et al. (2018) is the downer in the pile. Their plasma amino-acid panel barely hit 70 % sensitivity after stats cleanup. Baker et al. (2025) use that null result to temper the hype seen in the positive microbe papers.

Wang et al. (2025) mirrors the caution. That same-year review of presymptomatic markers also tells clinicians to stick with behavioral tools for now.

You may field parent questions about stool or urine kits sold online. This review gives you the evidence base to say, “Interesting, but unproven.” Keep watching the literature, keep collecting behavioral data, and treat biological tests only as experimental add-ons until bigger, longer studies prove they work.