GAS - Goal Attainment Scaling in Rehabilitation
GAS is a method of scoring the extent to which patient’s individual goals are achieved in the course of intervention. In effect, each patient has their own outcome measure but this is scored in a standardised way as to allow statistical analysis. Traditional standardised measures include a standard set of tasks (items) each rated on a standard level. In GAS, tasks are individually identified to suit the patient, and the levels are individually set around their current and expected levels of performance.
Goal attainment scaling (GAS) is an individualised health outcome measure that was first introduced by Kirusek and Sherman (1968) for assessing outcomes in mental health settings. This technique is found to be suitable for health problems which warrant a multidimensional and individualised approach to treatment planning and outcome measurement and has been used to demonstrate clinically important change in a variety of settings including elderly care (Stolee, Stadnyk, et al 1999; Stolee, Zaza, et al 1999), chronic pain (Zaza, et al 1999) and cognitive rehabilitation (Rockwood, et al 1997).
Formal assessment of goal attainment at the point of outcome assessment could provide an accurate indication of success in relation to the intended goals of treatment, both on the part of the patient and the clinician. The application of Goal Attainment Scaling also offers the opportunity of a single interval measure with which to assess response to intervention. This work began with the assessment of botulinum toxin intervention outcomes and has then developed for use in the wider inpatient rehabilitation environment.
How is GAS rated?
An important feature of GAS is the ‘a priori ‘ establishment of criteria for a ‘successful’ outcome in that individual, which is agreed with the patient and family before intervention starts so that everyone has a realistic expectation of what is likely to be achieved, and agrees that this would be worth striving for. Each goal is rated on a 5-point scale, with the degree of attainment captured for each goal area:
- If the patient achieves the expected level, this is scored at 0.
- If they achieve a better than expected outcome this is scored at:
- +1 (more than expected)
- +2 (much more than expected)
- If they achieve a worse than expected outcome this is scored at:
- -1 (less than expected) or
- -2 (much less than expected)
Goals may be weighted to take account of the relative importance of the goal to the individual, and/or the anticipated difficulty of achieving it.
GAS depends on two things – the patient’s ability to achieve their goals and the clinician’s ability to predict outcome, which requires knowledge and experience. A computerised programme calculates the baseline score, the T Score (achieved score) and change score. This is available as a stand alone Excel file or within the UKROC software.
Our department has led an international programme of work to encourage the consistent use of GAS in routine clinical practice. This has led to the development of the following resources:
- the GAS-Light – a simplified version of GAS designed to be usable in routine clinical practice
- a verbal rating scale for clinicians who prefer verbal descriptors to numbers
- a GAS calculation spreadsheet for calculating GAS T scores
- Scales to measure patient engagement in goal setting and their satisfaction with the goals selected
These resources are free and can be found below:
Please contact Elica Ming-Brown for further information on the next training date. Please note: GAS Training is not mandatory for UK ROC.
Our department has led an international programme of work to encourage the consistent use of GAS in routine clinical practice, including the GAS-Light – a simplified version of GAS designed to be usable in routine clinical practice.
Work is ongoing on using GAS to assess functional outcomes from focal interventions such as botulinum toxin intervention (BTX). In particular this work involves using GAS to measure the outcome of intervention related to upper limb spasticity and relate GAS outcome scores to the scores of other objective measures appropriate to this type of focal intervention.
BTX intervention does not stand alone and is used in conjunction with other therapy interventions. Therefore our projects in this area also aim to explore this complex intervention in more detail.
Application of goal attainment scaling
- Ashford S, Turner-Stokes L.,Evaluation of goal attainment in management of spasticity with botulinum toxin: Use of Goal Attainment Scaling to demonstrate functional gains, Physiotherapy Research International 2006; 11: 14-23
- Khan F, Pallant JF, Turner-Stokes L, Use of Goal Attainment Scaling (GAS) in rehabilitation for persons with Multiple Sclerosis, Archives of Physical Medicine and Rehabilitation 2008. 89(4):652-9
- Turner-Stokes L, Baguley I, De Graff S, McCrory P, Katrak P, Davies L, Hughes A., Goal attainment scaling in the evaluation of treatment of upper limb spasticity with botulinum toxin: a secondary analysis from a double blind placebo controlled randomised clinical trial, J Rehabil Med. 2010 Jan;42(1):81-9. doi: 10.2340/16501977-0474