Saliva Test for Autism?
Saliva Proteins May Aid Early Autism Diagnosis
Medscape Medical News
February 20, 2015

Proteins present in saliva might aid early diagnosis of autism spectrum disorders (ASDs), allowing for more prompt intervention, results of a pilot proteomic study suggest.

"We have identified potential biomarkers for autism diagnosis that are implicated in both heightened immune responses and gastrointestinal distress. This is consistent with current ideas about autism cause and comorbidities," co–lead investigator Alisa G. Woods, PhD, with the biochemistry and proteomics group, Clarkson University, Potsdam, New York, told Medscape Medical News.

The study was published online January 27 in the journal Autism Research.

Protein Signature
The researchers used nano liquid chromatography–tandem mass spectrometry to analyze the salivary proteome of six children with ASD and six typically developing children. All of the children were boys between the ages of 6 and 16 years.

They found that for nine proteins, levels were significantly elevated in the saliva of the children with ASD, and that for three proteins, levels were lower or the proteins were absent. For example, histatin-1 and statherin were not detected in saliva from children with ASD, suggesting that deficits in specific salivary proteins "may serve as biomarkers in ASD, comprising a signature that indicates ASD presence and risk."

The identified proteins primarily have functions in immune system responses or are elevated in people with gastrointestinal problems, consistent with observations that immune responses and inflammation may be increased in ASD, the investigators note.

"One of the most interesting proteins is called lactotransferrin, which we would really like to follow up on as a predictor of gastrointestinal problems in autism," said Dr Woods.

"Clinically, this marker might help to identify people on the spectrum with gastrointestinal problems. Since people with autism often have trouble communicating their symptoms, this could be particularly useful," she added.

By current estimates, ASD affects roughly 1 in 68 children in the United States. Diagnosis is based on behavioral assessments because there is currently no biological test for ASD. Identifying biomarkers for ASD would aid in earlier diagnosis and, in turn, earlier treatment, which has been shown to improve functional outcomes. The current study is an early step in that direction, the investigators note.

However, the fact that the study only included boys with ASD is a key limitation. The investigators plan to further study these protein differences in larger groups of children with autism and also in children with specific subtypes of autism.

"It is crucial that we validate these findings in larger numbers of individuals on the autism spectrum, who have also been extensively characterized in terms of behavior and coexisting conditions. This, of course, will be dependent on obtaining research funding," said Dr Woods.

Attractive Option
Echoing this sentiment, Matthew Siegel, MD, director of the Developmental Disorders Program at Spring Harbor Hospital in Westbrook, Maine, and clinical investigator at the Maine Medical Center Research Institute, told Medscape Medical News that "examining saliva is attractive due to its accessibility, but will need to be tested in much larger samples to see if there are useful results."

"The six children with ASD studied varied greatly in their degree of autism and language ability," he noted. "Examining a large, more homogeneous group, such as only individuals who are nonverbal with well-characterized ASD, would be an exciting strategy."

Dr Siegel also cautioned that "suggesting links between these very preliminary results and GI or immune system dysfunction in ASD is a big leap."

The study was supported by a grant from Shire Development, LLC, the Redcay Foundation, the David A. Walsh fellowship, the US Army research office, and the Sci-Fund Challenge 3 Donors. The authors report no relevant financial relationships.

Autism Res. Published online Jan. 27, 2015. Abstract