Investigating Plasma Amino Acids for Differentiating Individuals with Autism Spectrum Disorder and Typically Developing Peers.
Plasma amino-acid profiles alone are too shaky to sort autism from typical development.
01Research in Context
What this study did
Vargason et al. (2018) drew blood from the kids with autism and 30 typical kids. They measured 20 amino acids in the plasma. The team used computer models to see if the levels could tell the groups apart.
What they found
Three amino acids looked slightly different at first. After fixing for multiple tests, the gaps vanished. The best model got 70 % of autism cases right and 78 % of typical cases right. That error rate is too high for clinic use.
How this fits with other research
Cai et al. (2025) reached the same goal with stool bugs instead of blood. Their microbe profile hit 98 % accuracy, far above the 74 % AUC seen here. The amino-acid idea is sound, but the sample type matters.
Lecavalier et al. (2006) already warned that early plasma studies were shaky. The 2018 data confirm the call for tighter lab work. The older review pooled single markers; the new paper shows multivariate models still fall short.
Mulder et al. (2020) tied high maternal branched-chain amino acids to later autism risk. They studied moms, not kids, so the findings do not clash. Together they hint that amino-acid paths are involved, yet plasma levels at one time point are weak classifiers.
Why it matters
If a family asks about special blood tests for autism, you can say the plasma amino panel is not ready. Save them money and stress. Keep watching gut-microbe or neuro-imaging work instead, and keep diagnosing with gold-standard behavior tools.
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02At a glance
03Original abstract
BACKGROUND: Plasma amino acid measurements have been extensively investigated in individuals with autism spectrum disorder (ASD). Results thus far have been inconclusive as studies generally disagree on which amino acids are different in individuals with ASD versus their typically developing (TD) peers, due in part to methodological limitations of several studies. METHOD: This paper investigates plasma amino acids in children and adults with ASD using data from Arizona State University's Comprehensive Nutritional and Dietary Intervention Study. Measurements from 64 individuals with ASD and 49 TD controls were analyzed using univariate and multivariate statistical techniques. RESULTS: Univariate analysis indicated increased median levels of glutamate (+21%, p=0.014) and serine (+8%, p=0.043), and increased mean levels of hydroxyproline (+17%, p=0.018) for the ASD cohort, although these differences were insignificant after correcting for multiple comparisons. A multivariate approach was used to classify study participants into ASD/TD cohorts using Fisher discriminant analysis (FDA) and its nonlinear extension, kernel Fisher discriminant analysis (KFDA). Model fitting with FDA using all available measurements produced Type I and Type II errors of 27.0% and 27.8%, respectively. KFDA was most effective when using hydroxyproline, leucine, and threonine as inputs; however, leave-one-out cross-validation with this nonlinear model only resulted in 70.3% sensitivity and 77.6% specificity. CONCLUSIONS: The finding of elevated glutamate in ASD is in agreement with several other studies. Overall, however, these results suggest that plasma amino acid measurements are of limited use for purposes of ASD classification, which may explain some of the inconsistencies in results presented in the literature.
Research in autism spectrum disorders, 2018 · doi:10.1007/s00726-016-2332-y