Saliva diagnosis of autistic spectrum disorder by FT-IR spectroscopy

Autistic Spectrum Disorder (ASD), considered a neurological development disorder, is characterized by different degrees of deficit in communication, social interaction, and learning, accompanied by repetitive and stereotyped patterns of behavior. The diagnosis of ASD is extremely complex due to the unknown etiopathogenesis and the diversity of symptoms presented by the individuals. This study aimed to evaluate the effectiveness of Fourier Transform Infrared Spectroscopy (FT-IR) as a tool for the diagnosis of ASD in saliva. Saliva samples from 14 volunteers, 7 with ASD (G-A) and 7 Neurotypical (G-N) were analyzed. The collected samples were centrifuged, 20 µL of supernatant was deposited on calcium fluoride (CaF2) windows and dehydrated for 10 min. The FT-IR spectra were obtained by a spectrophotometer coupled to a microscope, in the spectral range of 4000 cm-1 - 900 cm-1 , with 32 scans, and spectral resolution of 4 cm-1 . A total of 112 spectra were collected, and their averages were submitted to Cluster analysis by the second derivative, aiming to group the results by similarity. FT-IR Spectroscopy was able to separate approximately 86% of the samples in the corrected group. The results showed an increase in bands related to proteins and hormones. Individuals diagnosed with ASD often have increased levels of stress, difficulty in interpersonal relationships, and reduced salivary flow compared to neurotypical individuals. ASD patients present a higher concentration of proteins and cortisol release in the saliva. FT-IR spectroscopy is a promising tool to differentiate saliva samples from ASD patients from neurotypical individuals.