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Factors That Affect Performance in Children with ASD on the VEP Task: Results from the ABC-CT Interim Analysis
Background: Autism Biomarkers Consortium for Clinical Trials (ABC-CT) aims to identify biomarkers to reliably measure treatment effects in autism spectrum disorder (ASD). This study focuses on analyses of Visual Evoked Potential (VEP) data collected during the EEG at two time points (baseline and 6 weeks). In the protocol, T2 visits were to occur 28-56 days after the T1 visit. Given that test retest reliability of the VEP (using ICC and presented at INSAR 2018) was .80 for the NT group and .68 for the ASD group, we examined the time between visits as a potential moderator of T1 and T2 response.
Objectives: To evaluate factors that impact data acquisition and the effect of the time of day and days between visits of T1 and T2 visits on the VEP EEG biomarker in participants with ASD.
Methods: Participants were 225 6- to 12-years-old children (TD: n=64; ASD: n=161) at 5 different sites who viewed videos of flickering checkerboards with central red fixation point while EEG was collected. Some of the outcome variables included total number of good trials, and P1 and N1 amplitude at Occipital Midline ROI.
Results: 79.5% children with ASD and 86% in the NT group provided valid data at T1 (χ2= 1.249, p = .26). At T2, 83.9% children with ASD and 86% NT children provided data (χ2= 3.883, p = .05). Time of day was coded as 1: A.M/2: P.M and was similar across both groups points (T1: χ2=.579, p=.447; T2: χ2 =3.33, p =.19).
Time between T1 and T2 visits and in whether the participant with ASD has valid T2 data collected (p=0.69) was not statistically significant. 10% children were excluded at T1 when tested at A.M, compared to 19% excluded at P.M, χ2 = 3.732, p = .053. At T2, 7.8% children were excluded when tested at A.M; compared to 12.2% excluded P.M (χ2 = .831, p = .36). Mean time between T1 and T2 did not differ for those children with and without T2 data. (p = .14)
Regression analysis showed that T2 performance was significantly predicted by both P1 and N1 amplitude in the ASD group at T1 (F=99.8, p < .001; F=135, p<.001). No effect of time between T1 and T2 or P1 variability was noted in T2 performance (t=-.041, p =.97); however, number of trials viewed at T2 did explain additional variability in the N1 amplitude (t=-1.921, p=.06).
Conclusions: Data loss was similar at T1 for both groups, however more ASD children provided data at T2, suggesting exposure to the protocol improved acquisition in ASD children. Testing time of visit time did not impact acquisition success consistently; however, T1 performance significantly predicted T2 performance in P1 and N1 amplitude. Overall, these analyses provide guidance on use of VEP in longitudinal clinical trials, specifically that children with ASD may perform better (higher acquisition rates) when given multiple times to attempt the EEG experiment; but that the distance between time-points (within a specified time frame) did not alter performance.