The Adaptation of Gilliam Autism Rating Scale-2 within an Omani Context: Some Initial Findings

Aim: The aim of the present study was to report some initial findings concerning the validity and reliability of the Omani version of the Gilliam Autism Rating Scale-2 (OM-GARS-2).

Sample: The sample of the study included 90 children aged 8-14 years and divided into two groups: Autistic group (n = 45), enrolled in two public centers of autism care in two governorates in Oman, and normal group (n =45), enrolled in two public schools in two governorates in Oman.

Raters Sample: A total of 8 teachers (4 males and 4 females) working in these centers rated students on the OM-GARS-2. And 7 teachers (4 males and 3 females) in these schools rated students on the OM-GARS-2. All ratings were performed over a three-week period.

Methodology: To answer the research questions, two types of reliability indictors were computed: (1) test-retest reliability, and (2) internal consistency reliability. Then, Pearson correlation coefficient was computed between students’ scores on OM-ABC which is studied by several researchers and the total score and the OM-GARS-2 subscales as well as total score. Finally, a multivariate analysis of variance (MANOVA) was conducted where group (autistic vs. normal) was set as an independent variable (factor) and the OM-GARS-2 subscales and Autism index was set as criterion variable to test the hypothesis that there would be one or more mean differences between groups.

Results: The results of the study showed the OM-GARS-2 had temporal stability and internal consistency reliability. The OM-GARS-2 had criterion (type concurrent) validity and discriminant validity.

Conclusion: To conclude, the reliability and validity indices of OM-GARS-2 are very similar to that of the original GARS-2 [1] and other studies conducted internationally.