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Goal Attainment Scale (GAS)
Availability
Availability: Guidelines for construction, administration and scoring of the Goal Attainment Scale are described in the following articles: Kiresuk et al., (1968), as well as Turner-Stokes (2009).
 
These websites may provide additional helpful information:
Classification
Exploratory: Cerebral Palsy (CP)
Short Description of Instrument
Construct measured: Individualized, patient-generated goals scored on a 5 point scale.
 
Generic vs. disease specific: Generic (not age specific or diagnosis specific)
 
Means of administration: Semi-structured interview
 
Intended respondent: The child or parent.
 
Background: The Goal Attainment Scale (GAS) was introduced in the 1960’s and used in a mental health setting. Many years later it began to appear in rehabilitation contexts, with continued and increasing use since then. The GAS has steadily gained popularity and has been used in numerous studies involving children with CP as an outcome measure following intervention.
Comments/Special Instructions
The original GAS uses a 5 point scale. Some authors have attempted to use a 3 and 7 point scale. Requires extensive therapist training and experience to set valid, accurate goals. There is no administration or scoring manual and thus the GAS is not administered or scored in a consistent manner among therapists or facilities. Reliability (therapst’s judgement of the impact of the intervention) and validity (ability of therapist to set realistic, accurate goals) may be difficult to establish. Recommend extensive training; utilization of therapists with at least one year of experience, use of independent raters to score outcomes may reduce bias, and supplement this measure with a standardized and objective tool.
Scoring
Three to five individualized goals are typically developed in collaboration with the child or parent. The goals are written with graded levels of difficulty representing predicted goal achievement; each level is described with measurable precision and detail. The achievement of each goal is measured using a five point scale. A score of 0 means the expected outcome was met, +2 the outcome exceeds expectations, and
-2 the outcome is less than expected. A single aggregated goal attainment score (a t- score) is calculated. A score of 50 means that the goals on average were obtained; a score >50 denotes a better that expected outcome.
 
Administration time: 45–60 minutes; retest and scoring approximately 15 minutes.
Rationale/Justification
Strengths/Weaknesses: The GAS is a flexible, individualized tool that can be used across diagnoses, age groups, and problem areas. It uses a client-centered approach to goal setting which has been shown to improve outcomes in children with CP. Validity and reliability issues are reported in the literature (therapist’s ability to accurately predict future performance; need for adequate training to achieve inter-rater reliability for scale development; need for independent raters to reduce bias). It is time consuming to develop goals.
 
Psychometric Properties: It is an individualized, patient generated scale and the content may not be the same from patient to patient. The psychometric properties for pediatric rehabilitation reported in a critical review (Steenbeek, 2007) are reported here (samples included 65 infants 3–30 months with motor delays, and 41 children ages 2–7 years with unilateral CP). The authors used the following definitions:  
Content reliability: Correlation in terms of textual content of GAS scales between two independent scale developers.
Interrater reliability: Correlation between the scores of two independent raters on the same GAS scale.
Content validity: Value of the textual content of GAS scales in relation to the relevance to the subject.
Concurrent validity: Correlation between the outcome in terms of GAS and other appropriate measures.
• Internal consistency: Not reported
Interrater reliability: Kappa coefficient of 0.89  
Concurrent validity: Low correlations with PDMS-2 and COPM
Content validity: (relevance of the goal to the subject): 77%–88% of therapists’ goals met criteria for content validity in a random sample of 10 goals
Sensitivity to change: The studies included in the critical review concluded that sensitivity to change depends upon whether the goals and levels of attainment represent clinically important changes. Two studies reported t-scores >50 (better than expected outcome). A study comparing the effect of BTX with a control found large GAS effect sizes.
Discriminative validity: GAS t-scores were able to discriminate between infants who were more or less motorically delayed. The GAS was able to detect changes within and between two groups
 
Overall, Steenbeek et al. (2007) concluded that the GAS appears to be a promising tool to measure change in heterogeneous populations with a variety of treatment goals. Reliability is largely unknown, and training to ensure reliability is necessary, as are descriptions of training should be reported in publications. Also, the validity of the GAS is ambiguous: concurrent validity is low, however its individualized approach allows a therapist to measure exactly what needs to be measured.
References
Kiresuk TJ, Sherman RE. Goal attainment scaling: A general method for evaluating comprehensive community mental health programs. Comm Mental Health J. 1968;4(6):443–453.   
 
Steenbeek D, Ketelaar M, Galama K, Gorter JW. Goal attainment scaling in paediatric rehabilitation: a critical review of the literature. Dev Med Child Neurol. 2007;49(7):550–556.  
 
Additional References:
 
Cusick A, McIntyre S, Novak I, Lannin N, Lowe K. A comparison of goal attainment scaling and the Canadian Occupational Performance Measure for paediatric rehabilitation research. Pediatr Rehabil. 2006;9(2):149–157.  
 
King GA, McDougall J, Palisano RJ, Gritzan J, Tucker MA. Goal Attainment Scaling. Phys Occup Ther Pediatr. 2000;19(2):31–52.  
 
Palisano RJ, Haley SM, Brown DA. Goal attainment scaling as a measure of change in infants with motor delays. Phys Ther. 1992;72(6):432–437.
 
Palisano RJ. Validity of goal attainment scaling in infants with motor delays. Phys Ther. 1993;73(10):651–658.  
 
Steenbeek D, Gorter JW, Ketelaar M, Galama K, Lindeman E. Responsiveness of Goal Attainment Scaling in comparison to two standardized measures in outcome evaluation of children with cerebral palsy. Clin Rehab. 2011;25(12):1128–1139.  
 
Turner-Stokes L. Goal attainment scaling (GAS) in rehabilitation: a practical guide. Clin Rehab. 2009;23(4):362–670.
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