The development of a brief screener for autism using item response theory

Caroline Mårland,Gitta Lubke,Thomas Nilsson,Christopher Gillberg,Maria Råstam,Alessio Degl’Innocenti,Sebastian Lundström

doi:10.1186/s12888-019-2333-y

Abstract

BackgroundBrief screening instruments focusing on autism spectrum disorder (ASD) that can be administered in primary care are scarce; there is a need for shorter and more precise instruments. The Autism–Tics, AD/HD and other Comorbidities inventory (A-TAC) has previously been validated for ASD reporting excellent validity. This study aims to determine the psychometric properties of each item in the ASD domain (17 items) in the A–TAC using item response theory (IRT), and thereby construct and validate a short form that could be used as a screening instrument in the general population.MethodsSince 2004, parents of all 9-year-old Swedish twins have been invited to participate in a telephone interview in the Child and Adolescent Twin Study in Sweden (CATSS). The CATSS is linked to the National Patient Register (NPR), which includes data from in- and outpatient care. Data on ASD (A-TAC) collected in CATSS were compared with diagnoses from the NPR. Diagnoses that had been made both before (previous validity) and after (predictive validity) the interviews were included. The sample was divided into a developmental sample and a validation sample. An IRT model was fitted to the developmental sample and item parameters were used to select a subset of items for the short form. The performance of the proposed short form was examined in the validation sample by the use of receiver operation characteristic curves.ResultsFour items which were able to discriminate among individuals with more autism traits were deemed sufficient for use in the short form. The values of the area under the receiver operating characteristic curve for a clinical diagnosis of ASD was .95 (previous validity) and .72 (predictive validity).ConclusionsThe proposed short form with 4 out of the original 17 items from A-TAC, showed excellent previous validity while the predictive validity was fair. The validity of the short form was in agreement with previous validations of the full ASD domain. The short form can be a valuable screening instrument in primary care settings in order to identify individuals in need for further assessment and for use in epidemiological studies.

Highlights

Brief screening instruments focusing on autism spectrum disorder (ASD) that can be administered in primary care are scarce; there is a need for shorter and more precise instruments
The aims of this study were to: (a) determine the psychometric properties of each item in the ASD domain in A-TAC using item response theory (IRT), (b) construct a short form that could be used as a screening instrument in the general population, and (c) validate the proposed short form and determine cut-off values
The result indicates that the ASD domain can discriminate among subjects in the far end of the autism trait continuum and that the higher response categories are only endorsed for subjects who have a higher than average level of ASD

Summary

Introduction

Brief screening instruments focusing on autism spectrum disorder (ASD) that can be administered in primary care are scarce; there is a need for shorter and more precise instruments. For ASD, a number of instruments are available such as the Modified Checklist for Autism in Toddlers (which includes 23 items, reported sensitivity/specificity: .87/.99) [7]), the Autism Spectrum Screening Questionnaire (27 items [8], .62/.90 [9]), the Social Communication Questionnaire (40 items [10], .85/.75 [11]), the Social Responsiveness Scale (65 items, .85/.75 [12]), and the Autism–Tics, ADHD and other Comorbidities inventory (A–TAC, 17 items, .96/.88 [13]) These instruments range between 17 and 65 questions and even though they might be considered to be brief, there is a need for shorter and reliable instruments. An initial screening should be broad and tap into the whole child and adolescent psychiatric field in order to allocate the child to the most suitable assessment service where a full clinical investigation is conducted

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