Assessment of the Olfactory Trait in Children with Autism Spectrum Disorders Using an Olfactory Software Application

Background:  Olfaction is regarded as one of the most important diagnostic or prognostic markers in a number of neuropsychiatric disorders. Abnormal reactions to olfactory stimuli in children with autism spectrum disorder (ASD) have been described in several clinical studies using sensory questionnaires. However, laboratory-based sensory psychophysical studies to investigate the olfactory trait in children with ASD using olfactory testing have produced inconsistent results. Previous research has failed to show significant correlations between autism severity and laboratory data. Adaptation is an important process, allowing individuals to adjust to changes in their environment. Few studies measure olfactory adaptation in children with ASD. Olfactory laboratory tests have provided limited information about such abnormalities in those with ASD.

Objectives:  In this study, we used an olfactory measurement that uses a pulse ejection system as well as olfactory application software, which we developed. Previous olfactory measurement techniques cause problems with scents scattering and lingering in the air, making accurate measurements impossible. We have attempted to resolve these problems by using a display with a pulse ejection system to present a scent for a short duration at the picoliter level. Using very small quantities of scent reduces lingering scents during measurement and makes it more difficult for olfaction to adapt compared to existing measurement techniques. We also developed an olfactory application software that can measure the adaptation to changes in odor. This study examined adaptation to changes in odor using a pulse ejection system and this new software application in a sample of children with ASD.

Methods:  The inclusion criteria were chronological age of 10 to 16 years and previous diagnosis of high-functioning ASD. All participants satisfied the diagnostic criteria for ASD in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (American Psychiatric Association, 2013). To exclude other psychiatric diagnoses, the Mini-International Neuropsychiatric Interview for Children and Adolescents was conducted by a licensed pediatric psychiatric clinician. Thirteen children with ASD participated. Adaptation to changes in odor was assessed using the olfactory measurement system with olfactory display, which uses a pulse ejection system, and the new software application. We used isoamyl acetate and ethyl butyrate flavor for the odorants. The odors of isoamyl acetate and ethyl butyrate flavor were released for 20 seconds each by the display using a pulse ejection system. We investigated whether participants were able to recognize the change of the odorants using touch panel display controlled by the olfactory software application. We used the Childhood Autism Rating Scale (CARS) to measure the severity of the autistic trait. Statistical analysis was performed using the Statistical Package for the Social Sciences, version 15.0.

Results:  Seven participants passed, and six did not. The total score and the “Taste, Smell, and Touch Response and Use” score on the CARS were lower in the group who passed than in the group who did not (p < 0.01).

Conclusions:  Adaptation to changes in odor may be connected with the severity of autism. Implications for further research are discussed.