An Initial Evaluation of the Validity of the Gilliam Autism Rating Scale-Third Edition (GARS-3) in a Clinical Sample Katie A. Hastings and Jonathan M. Campbell University of Kentucky Department of Educational, School, and Counseling Psychology Results Background Information Third party rating scales may be used to support diagnostic decision making in Autism Spectrum Disorder (ASD) diagnostic evaluations. One such measure is the Gilliam Autism Rating Scale-Third Edition (GARS-3; Gilliam, 2014). The GARS-3 is a standardized norm-referenced instrument designed to assist in the diagnosis of ASD. The GARS-3 is keyed to correspond with DSM-5 diagnostic criteria and was standardized with a sample of 1,859 individuals with ASD 3 to 22 years of age. Gilliam (2014) provides psychometric support for the GARS-3 as evidenced by internal consistency of .79 - .94 for GARS-3 subscales and .93 - .94 for GARS-3 Autism Index scores. Gilliam (2014) also reports criterion-related validity in support of the GARS-3 as evidenced by significant correlations between the GARS-3 Autism Index and (a) the Childhood Autism Rating Scale, Second Edition (CARS-2; r = .68) and (b) Autism Diagnostic Observation Schedule (ADOS; r = .69). In the present study, authors examined relationships between the GARS-3 and the ADOS-2 and CARS-2 in a clinically referred sample. Authors also tested whether GARS-3 Autism Index scores differed between individuals diagnosed with ASD and those not diagnosed with ASD who were referred to an autism diagnostic specialty clinic. Research Questions 1. How well does the GARS-3 correlate with other commonly used diagnostic measures of ASD? 2. Do GARS-3 scores differ significantly for individuals diagnosed with ASD and individuals not diagnosed with ASD? Participant Characteristics (N = 20)
Gender Race
Ethnicity Diagnosis Age (yr) IQ score
Variable
n
%
Male Female
16 4
80 20
Caucasian African-American Other
16 3 1
80 15 5
Non-Hispanic Hispanic
19 1
95 5
ASD Non-ASD
12 8
60 40
Min
Max
M
SD
Correlations between GARS-3 Index, CARS-2 T and Raw scores, and ADOS-2 Comparison scores (N=20) GARS-3
CARS-2 Raw
CARS-2 T
GARS-3
---
CARS-2 Raw
-.10
---
CARS-2 T
-.09
.97**
---
-.08
.67**
.65**
ADOS-2 Comp Note:
a
a
ADOS-2 Comp
a
---
= For ADOS-2 Comparison correlations, n = 17. ** = Correlation is significant at the .01 level.
Results and Discussion CARS-2 Raw Scores differed across ASD (M = 31.00) and non-ASD groups (M = 21.88), t(18) = 3.42, p < .01. ADOS-2 Comparison scores differed across groups (ASD M = 6.40; Non-ASD M = 1.86), t(15) = 5.56, p < .001. 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. 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 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. Limitations of our study include a small sample size and use of clinically referred sample of participants. To further understanding of GARS-3 validity, further evaluation should be conducted with larger samples across varied settings. References Gilliam, J. E. (2014). Gilliam Autism Rating Scale – Third Edition [Rating scale]. Austin, TX: Pro-Ed.
3.25 46
22.7 112
8.23 80.0
5.6 20.4
Correspondence concerning this presentation should be addressed to: Katie Hastings, Department of Educational, School, and Counseling Psychology, University of Kentucky, Lexington, Kentucky 40506-0017, E-mail:
[email protected]
