Constructs Assessed by the GARS-2: Factor Analysis of Data from the Standardization Sample

Abstract

The GARS-2 (Gilliam 2006) is widely used for autism screening; however, the validity of its three conceptually-derived subscales has not been evaluated. In this study, exploratory (EFA) and confirmatory (CFA) factor analyses of data from matched subgroups of the standardization sample did not support the GARS-2 subscale structure. EFAs identified four factors in the model development subgroup (n = 496): stereotyped/repetitive behavior, stereotyped/idiosyncratic language, word use problems, and social impairment. CFAs supported this model in the replication subgroup (n = 494). Findings suggest that the GARS-2 subscales have limited clinical utility and that the Autism Index should be interpreted with caution. Although more research is needed, the clinical utility of the four empirically-derived scales may be limited by factors related to item content and test development procedures.

A National Study of Autistic Symptoms in the General Population of School‐Age Children and Those Diagnosed with Autism Spectrum Disorders

“…The two factors correlated at r = .63. Merging of social, communication, and odd behaviors into one factor and self-regulation as a second is inconsistent with conceptualizations of the ASD, as well as most empirical findings (e.g., Austin, 2005;Kamp-Becker, Ghahreman, Smidt, & Remschmidt, 2009;Matson, Boisjoli, & Dempsey, 2009;Pandolfi, Magyar, & Dill, 2010). Taking into consideration the scree plot data and the inadequate fit of these items to factors, we considered this solution to be under-factoring.…”

Factor Structure, Internal Consistency, and Screening Sensitivity of the GARS-2 in a Developmental Disabilities Sample

“…Measures used in assessments for ASD have been categorized along different dimensions including purpose (i.e., screening versus diagnosis) and level of training needed for administration/scale completion (i.e., professional/trained raters versus untrained raters [ 4 , 5 ]). At present, two measures recognized for their diagnostic accuracy are the Autism Diagnostic Interview-Revised (ADI-R [ 6 ]) and Autism Diagnostic Observation Schedule-Second Edition (ADOS-2 [ 7 ]).…”

“…Although informant rating scales may not be diagnostic on their own, they can contribute important information as part of screenings and/or comprehensive assessments [ 2 , 10 ] and can assist with differential diagnosis [ 11 ]. This is especially useful when the measure assesses multiple constructs, is keyed to a diagnostic framework (e.g., DSM-IV or DSM-5 ), and provides a quantification of symptoms [ 3 , 5 , 8 ]. Informant rating scales may offer advantages over professionally administered scales (e.g., ADI-R) such as greater efficiency and reduced training.…”

“…Despite their potential, rating scales may have limitations (e.g., lack of alignment between scale items and diagnostic criteria, inadequate psychometric properties) that reduce their validity [ 4 ]. These potential problems have led to recommendations for psychometric studies of commonly used rating scales [ 4 , 5 ].…”

“…For noncommunicative individuals, the Communication subscale is omitted and the Autism Index is calculated based on the other two subscales. While the GARS-2 item content is very similar to the original scale items [ 5 ], the test author reported improvements including the rewriting of some items to increase clarity, elimination of the Early Development scale (replaced by a parent interview not included in scoring), renorming based on the 2000 census, and modification of the guidelines for score interpretation [ 12 ].…”