Goal Attainment Scaling (GAS)

Health professionals will use GAS to help people with cerebral palsy work out goals to work on during therapy or intervention. Setting personal goals can help focus the attention and energy of the client and their health care provider. This, in turn, may increase motivation levels and help someone achieve improvements in different areas of their life¹. Importantly, a second GAS is completed after therapy or intervention to measure whether the goals have been achieved.

GAS can be used by people of any age, and with cerebral palsy of any severity to measure the outcomes for a wide range of interventions and services². The health professional completes the assessment with the client, their parent or family member - or both people together.

The health professional works with the client and their family to identify goals that matter to them. Goals may be related to participating in life situations, such as going to youth groups or the movies. Goals may also be related to everyday activities such as improving handwriting, eating with a knife and fork, riding a bike or catching a ball. Health professionals play an important role in helping the person and family select goals that are realistic and achievable. After completing the therapy or intervention, the health professional will help the person and their family determine how well their goals were achieved.

Completing a GAS assessment usually takes between 20 and 40 minutes.

Training

While there is no specific manual or website providing training in using GAS, a number of resources are available to assist health professions in working with clients to develop reliable, valid and effective goals (see references 3 to 5 below^3-5). Health professionals will need education, support and the opportunity to practice goal setting. Ideally the GAS goals that they set, when starting to use this assessment, should be peer reviewed to assist the health professional in developing reliable and valid goal scaling⁶.

Cost

There is no cost for using GAS. Developing GAS goals can be time consuming but, ultimately, may save time for the health professional, client and their family, as it is more likely that they will have a greater ability to remain focused during intervention^1,2.

Method

GAS is a client-centred, criterion referenced measure. When using this assessment, the Canadian Occupational Performance Measure can be used in combination to help the client identify priorities, which are then written as GAS goals. Up to five of the most important goals are scaled on a five-point scale. Usually, the current level of ability for each goal is given a score of minus 2 (-2) and the ability level (or goal) that is desired or expected after intervention is given a score of zero. Progress toward, but not achieving the expected outcome is scaled -1 (less than expected outcome), and two levels of achievement which exceed the expected outcome are scaled as +1 (greater than expected) and +2 (much greater than expected). Occasionally 6- or 7- point scales are used².

After therapy or intervention, the health professional, with the person and family, will work out how well each goal has been achieved. For each goal, a score will be generated according to the scale listed above. It will be clear if the person has achieved each goal (score = 0), progressed, but less well than expected (and scored -1) or has achieved the goal better (+1) or much better than expected (+2). These scores can be collated into totals which indicate the client’s average goal achievement.

Things to note

There is considerable debate around the best way to collate the scores from individual goals, but no recognised best-practice approach. A number of references below discuss this debate and provide suggestions^2,3,7,8,9.

There is no standardised process for developing, scaling and scoring GAS – making it difficult to evaluate its psychometric properties. Both reliability and validity, however, are optimised when the health professional takes a collaborative approach with the client and their family to develop goals¹⁰.

The goals that are set should be articulated as observable behaviours and written in present tense language, using the SMART format^4,11. SMART goals are Specific, Measurable, Achievable, Relevant/Realistic and have a specified Timeframe for achievement.

Psychometric properties reviewed

Validity – little work has been completed on the validity of GAS. Low to moderate correlations exist between GAS and standardised assessments, such as the Pediatric Evaluation of Disability Inventory (PEDI)⁷. This is expected, however, because PEDI contains a range of items, many of which may not be relevant to a person’s goals for therapy. GAS, on the other hand, contains a limited range of very specific items⁵.

Reliability – inter-rater and intra-rater reliability are well established for GAS⁸ but no work appears to have examined test-retest reliability.

Responsiveness – this is considered a strength – probably because GAS is focused on issues that are relevant to the client, are targeted by intervention and therefore most likely to respond to the intervention⁸.