Objective: To explore the characteristics of P300 event-related potential in children with autism spectrum disorders (ASD) of different severity levels and to analyze the correlation between its latency or amplitude and the severity of ASD.

Methods: The study included 100 children with ASD who visited the Shenzhen Luohu District Maternal and Child Health Hospital from October 2022 to October 2023. Children with ASD were divided into 2 groups (mild to moderate group and severe group) according to the scoring results of the Childhood Autism Rating Scale (CARS). We compared the characteristics of P300 event-related potential latency and amplitude at midline sites (Fz, Cz and Pz) between the two groups. We explored the relationship between latency or amplitude and the severity of ASD in children.

Results: The study included a total of 100 children with ASD, including 59 in the mild to moderate group and 41 in the severe group. There was no statistically significant difference in age, gender, family history, and medication treatment history between the two groups. (P>0.05). Factors such as the latency of P300 at the Fz, Cz, and Pz midline loci (P values of <0.001, 0.008, and 0.004, respectively) and the amplitude of P300 at the Cz and Pz midline loci (P values of <0.001 and 0.004, respectively) were statistically significant between the two groups according to the univariate logistic analysis. The latency value of Fz locus P300 might be a risk factor for the severity of ASD [OR＝1.018 (95% CI: 1.008-1.028), P<0.001], while the amplitude value of Cz locus P300 might be a protective factor for the severity of ASD [OR＝0.505 (95% CI: 0.352-0.726), P<0.001] based on the multiple logistic regression analysis. The P300 latency values of various midline loci in ASD children were positively correlated with CARS scores (all P<0.01), and the P300 amplitude values of Cz and Pz midline loci in ASD children were negatively correlated with CARS scores (all P<0.001) according to the correlation analysis of CARS scores of enrolled ASD children.

Conclusion: There are significant differences in the expression of P300 event-related potential in children with ASD of different severity levels. Children with ASD of higher severity have lower P300 latency at each midline locus, and lower P300 amplitude at Cz and Pz midline loci; The latency value of Fz locus P300 may be a risk factor for the severity of ASD, while the amplitude value of Cz locus P300 may be a protective factor for the severity of ASD. The latency and amplitude detection of P300 event-related potential can provide an objective neurophysiological basis for evaluating the severity of ASD in children.