An Initial Evaluation of the Validity of the Gilliam Autism Rating Scale-Third Edition (GARS-3) in a Clinical Sample
Objectives: The authors conducted an initial evaluation of the validity of the GARS-3 by correlating scores with well-established measures of autism symptomatology. Investigators also contrasted GARS-3 scores between individuals who met DSM-5 diagnostic criteria for ASD and those individuals who did not.
Methods: Participants were 20 individuals (M age = 8.23 yr; 80% Male; 80% Caucasian; 12 diagnosed with ASD, 8 diagnosed with another DSM-5 disorder) who participated in comprehensive diagnostic evaluation at a training clinic at a land grant university in the Southeast U.S. Diagnostic evaluation was established using results from the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) and CARS-2. Caregivers completed the GARS-3 as part of the diagnostic evaluation; GARS-3 ratings were collected for the purposes of research and were not used in diagnostic decision making.
Results: Preliminary results indicate significant relationship between ADOS-2 Module 3 Total Scores and CARS-2 T Score, r(3) = .87, p < .05. ADOS-2 Module 2 Total Score also correlated highly with the CARS-2 T Scores, r(5) = .74, p < .05. ADOS-2 Module 3 Total Score and the GARS-3 Autism Index were not correlated, r(3) = -.04, ns. CARS-2 T Score and the GARS-3 Autism Index were also uncorrelated, r(18) = .06, ns. CARS-2 T Scores differed across ASD and non-ASD groups, t(18) = 3.42, p < .05. Individuals with ASD diagnosis (n = 12) earned similar GARS-3 Autism Index scores (M = 79.92; SD = 18.62) to individuals without ASD diagnosis (n = 8; M = 93.75; SD = 10.63); t(18) = -1.90, ns.
Conclusions: Preliminary results suggest weak relationships between the GARS-3 Autism Index Score and the ADOS-2, and the GARS-3 Autism Index Score and CARS-2 T Score. ADOS-2 and CARS-2 T scores differed across diagnostic groups, with individuals with ASD earning significantly higher scores. GARS-3 Autism Index scores, however, did not differ between groups with ASD and those without ASD. Initial findings warrant caution in using the GARS-3; however, larger samples are needed to fully document the utility of the GARS-3 in diagnostic evaluation.
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