"The present study supports early recognition of a distinctive metabolic profile in DBS [dried blood spots] whose distinguishing features suggest a reduced flux through the mitochondrial fatty acid β-oxidation pathway and provides insight into concealed molecular mechanisms determining ASD [autism spectrum disorder]."
So said the findings reported by Rita Barone and colleagues  including some notable names on the authorship list with some previous interest in acyl-carnitines and autism (see here), one important source of discussions in the Barone study.
Some basics from the Barone study: "A targeted panel of 45 ASD analytes including acyl-carnitines and amino acids extracted from DBS was examined in 83 children with ASD... and 79 matched, neurotypical (NT) control children." Autism was confirmed as autism in the 83 autistic children, also including the application of some important exclusionary criteria such as a "positive history for mitochondrial disease or known medical conditions including autoimmune disease and inflammatory bowel diseases (IBD)/celiac disease." I was also happy to see that researchers screened for 'possible autism' in their control participants too: "The Social Communication Questionnaire was used to screen and exclude autism in TD [typically developing] children."
Although the Barone study was a study predominantly analysing dried blood spot samples (a sample medium that has always been slightly under-utilised in research circles), researchers did also look at urine and blood samples obtained during the course of their study. They reported some interesting observations as a consequence of analysis; notably that: "Twenty-five out of 40 studied [autistic] subjects (62.5%) had significantly decreased blood Vitamin D3 levels with normal Ca/P ratio." Decreased vitamin D levels are no stranger to autism (see here and see here).
Insofar as the 'ASD analytes' results, we are told that 8 acyl-carnitines were significantly increased in the autism group compared to the control (not autism) group. I'm not going to bore you with the specific details but suffice to say the list of compounds was pretty robust and "confirm the same, unique pattern of acyl-carnitine profile" as noted in other studies with other groups. Researchers also mention how one particular amino acid - citrulline - was also significantly increased in the autism group compared to controls. They talk about how: "Blood citrulline level is considered a biomarker of gastrointestinal mucosal surface and enterocyte integrity" among other things and could have some implications for that and other 'effects'.
And then something else: "The present study confirms that patients with ASD may show a distinct metabolic profile, demonstrating that this can be used to identify a subset of ASD patients with respect to TD at younger ages." I'm always a little bit wary of studies talking about biomarkers and autism (see here for another example) but the important use of the word 'subset' denoting how autism is a label covering significant heterogeneity makes me feel a little easier about such sentiments (see here and see here) albeit with much more study being required.
 Barone R. et al. A Subset of Patients With Autism Spectrum Disorders Show a Distinctive Metabolic Profile by Dried Blood Spot Analyses. Front Psychiatry. 2018 Dec 7;9:636.