Convergent and Divergent Validity of the Early Video Guided Autism Screener (EVAS) in a Clinically-Referred Sample

Background: Although ASD can be detected as early as age 14 months (e.g., Landa, Gross, Stuart, & Faherty, 2013; Landa, Holman, & Garrett-Mayer, 2007), the average age of diagnosis is four years (ADDM, 2014). The American Academy of Pediatrics (AAP) recommends universal screening at ages 18 and 24 months, though screening and referral practices are inconsistent due to cost, lack of staff training, and time needed for screening. Access to a low-cost screening tool to promote completion of screening and referral can lead to earlier access to diagnosis and treatment. Existing autism-specific tools demonstrate modest sensitivity and specificity. The Child Behavior Checklist (CBCL; Achenbach & Rescorla, 2000) has been evaluated as an efficient means to screen for ASD as well as other possible comorbidities, given the already widespread use of this tool. Several studies have shown that the Withdrawn and Pervasive Developmental Problems scales of the CBCL 1.5-5 version are useful in screening young children for ASD (Havadal et al., 2015; Muratori et al., 2011; Sikora et al., 2008).

Objectives: To examine the construct validity (i.e., divergent and convergent validity) of the EVAS in a clinically referred sample, relative to the CBCL, which shows growing evidence as a potential ASD screening tool.

Methods: Sample of 178 children aged 18-48 months (83.7% male, 52.2% White, Mean age = 33.24 months, SD = 8.43 months) referred to an autism specialty center for diagnostic evaluation due to concerns for possible ASD. Parents completed the EVAS and CBCL online during the clinic intake process prior to their diagnostic visits. A clinical best estimate (CBE) was assigned by the diagnosing clinician following the evaluation.

Results: To account for multiple comparisons, a Bonferroni correction was applied to evaluate differences between the EVAS cut-off and each CBCL syndrome and DSM-oriented scale (.05/13 = .0038). Using this correction, only the CBCL Withdrawn (t(176) = 3.18, p = .002) and PDD (t(176) = 3.23, p < .001) subscales differed according to EVAS screening results (See Figure 1). Children who screened positive on the EVAS had T scores over 1 SD higher on the Withdrawn and PDD scales than children who screened negative on the EVAS, suggesting convergent validity of EVAS screening results. Children who screened positive and negative on the EVAS were similar in terms of all other CBCL scales, child age, and child race (all p> .0038), suggesting evidence for divergent validity. See Table 1 for a summary of results.

Conclusions: Results provide evidence for construct validity of the EVAS, suggesting it is a valid tool to measure ASD-related concerns. Importantly, results suggest that the EVAS items are specific to ASD, rather than associated comorbidities (e.g., attention or affective concerns).  Thus, the EVAS has strong potential as an ASD-specific screening tool.