The Broad Autism Phenotype–International Test (BAP-IT): A two-domain-based test for the assessment of the broad autism phenotype

The broad autism phenotype is the phenotypic expression of the primary characteristics of autism. However, currently available tests do not agree with the two-domain operationalization of broad autism phenotype or autism, and their internal structure has shown instability across applications. This study presents the Broad Autism Phenotype–International Test, the first such test designed to target a two-domain operationalization in Spain and the United Kingdom. A broad pilot study was conducted in three community samples, two from Spain (ES1, N = 970; ES2, N = 460) and one from the United Kingdom ( N = 530). The Broad Autism Phenotype–International Test consists of 20 items distributed into the SOCIAL-BAP and RIRE-BAP dimensions, representing the seven autistic subdomains. Common factor approaches were used to find a simple and invariant factor structure between countries. The Broad Autism Phenotype–International Test presents full metric invariance between two Spanish samples, partial invariance between countries, and adequate omega reliability estimation. Evidence-based results on the relationships of the SOCIAL-BAP and RIRE-BAP to other variables (the Social Responsiveness Scale-2 and the Broad Autism Phenotype Questionnaire) support the interpretation of its scores for the intended uses. The evidence provided in this article shows that the Broad Autism Phenotype–International Test functions adequately compared to other available broad autism phenotype tests, such as the Broad Autism Phenotype Questionnaire. Lay abstract The broad autism phenotype refers to a group of behaviors related to autism spectrum disorder, but that appear to a lesser extent. Its assessment has been performed through outdated broad autism phenotype/autism spectrum disorder definitions and tests. To address this problem, this study presents the development of a new test, the Broad Autism Phenotype–International Test, a 20-item measure consisting of two dimensions, SOCIAL-BAP and RIRE-BAP, targeting the two-domain operationalization of autism spectrum disorder in Spain and the United Kingdom. Unlike the Broad Autism Phenotype Questionnaire, this test received empirical support as a quick and effective broad autism phenotype measure that can facilitate both broad autism phenotype/autism spectrum disorder research and interventions. This is the first step to studying the BAP in several Spanish and English-speaking countries.