Outcome measurement is how allied health clinicians show whether NDIS therapy is making a difference. Two individualised, client-centred tools are widely used: Goal Attainment Scaling (GAS), which scores progress against a person's own goals on a five-point scale, and the Canadian Occupational Performance Measure (COPM), which rates performance and satisfaction on the activities a person prioritises. Both suit speech pathology and occupational therapy.
Key takeaways
- Outcome measurement turns "we did therapy" into "here is the change against goals."
- Goal Attainment Scaling scores progress from -2 to +2 against individually written goals ().
- The COPM rates performance and satisfaction on 10-point scales through a semi-structured interview ().
- GAS and the COPM work together: the COPM helps identify priorities, which become GAS goals.
- Both have evidence supporting their use, and known limitations that need disciplined application.
Why does outcome measurement matter in NDIS therapy?
Because it demonstrates value, guides clinical decisions and respects the participant's goals. The NDIS funds supports that are expected to be effective and beneficial, so being able to show whether a person is progressing toward their goals is central to good practice and to plan reviews. Outcome measurement also keeps therapy honest: it can reveal when an approach is not working and should change.
Individualised measures are particularly suited to disability services, because two people with the same diagnosis may have entirely different priorities. Standardised norm-referenced tests have their place, but they often miss the specific, personally meaningful goals that matter most to a participant.
What is Goal Attainment Scaling (GAS)?
Goal Attainment Scaling is an individualised, criterion-referenced method for measuring progress against goals written specifically for that person. For each goal, the clinician and participant define a set of outcome levels in advance, scaled on a five-point scale: typically the current or baseline level is set around -2, the expected outcome is 0, and better-than-expected outcomes are +1 and +2 ().
Because the goal and its levels are written for the individual, GAS can capture meaningful change that a standardised test would not detect. A scoping review of GAS in randomised controlled trials confirmed the -2 to +2 structure and noted that GAS is valued for assessing participant-important priorities, while cautioning that inconsistent application raises the need for greater standardisation to protect its validity and reliability ().
What is the Canadian Occupational Performance Measure (COPM)?
The COPM is a client-centred outcome measure that identifies the everyday activities a person needs to, wants to, or is expected to do, and then rates them. Using a semi-structured interview, the clinician helps the person identify up to five priority activities, which are scored on two 10-point scales: performance (how well they do the activity) and satisfaction (how satisfied they are with their performance). For young children or people with communication difficulties, a family member or carer can complete it ().
The COPM is the most widely used outcome measure in occupational therapy internationally, with over 500,000 completed each year, used in more than 50 countries and available in over 40 languages (). Re-rating the same activities later shows change over time.
How do GAS and the COPM work together?
They complement each other neatly. The COPM is well suited to surfacing and prioritising what matters to a person; GAS is well suited to defining graded, measurable levels of success for those priorities. In practice, clinicians often use the COPM to identify priorities, which are then written up as GAS goals ().
How do you use them well in speech pathology and OT?
The same disciplined steps apply to both speech pathology and occupational therapy:
- Collaborate on goals with the participant (and family/carer) so they are genuinely theirs.
- Write goals that are specific, observable and measurable.
- Set a clear baseline before intervention starts.
- For GAS, define each outcome level in advance; for the COPM, record initial performance and satisfaction scores.
- Re-measure at agreed points and interpret change with the participant.
- Use the result to decide whether to continue, adjust or conclude the approach.
For a speech pathologist, a GAS goal might grade a child's use of a communication strategy across settings; for an occupational therapist, the COPM might track a young person's independence and satisfaction with morning self-care. Both are routine in how our and teams plan and review supports, and they sit alongside our work where goals are equally individualised.
What does the evidence say about GAS and the COPM?
Both have supportive evidence and clear caveats, which is why method matters.
For GAS, an analysis of its responsiveness in controlled trials found that GAS detected meaningful change in a patient-centred care initiative, and that using more than one goal improved responsiveness compared with a single goal (). The scoping review above supports its value while stressing consistent, standardised application ().
For the COPM, a systematic review in geriatric rehabilitation reported good test–retest reliability, moderate inter-rater reliability, good content and construct validity, and moderate responsiveness (). As with any individualised measure, results depend on how carefully the tool is administered and interpreted.
The practical lesson: these tools are only as good as the goals and baselines behind them. Done well, they give a credible, participant-centred account of progress; done carelessly, they produce numbers without meaning.
Evidence at a glance
Frequently asked questions
Why not just use standardised tests?
Norm-referenced tests compare a person to a population and are useful for some purposes, but they often miss individually meaningful goals. Individualised measures like GAS and the COPM capture the specific, personally important change that matters in NDIS therapy. Many clinicians use both.
Is GAS or the COPM better?
Neither is universally better; they do different jobs. The COPM is strong for identifying and prioritising activities, while GAS is strong for grading expected outcomes. They are frequently used together, with COPM priorities written up as GAS goals.
Can families help complete these measures?
Yes. The COPM can be completed by a family member or carer when a participant cannot self-report, and GAS goals are written collaboratively. Involving families improves relevance and accuracy.
Do these tools prove therapy worked?
They provide structured evidence of change against goals, not proof of cause, and outcomes are never guaranteed. Careful baselines, clear goals and honest interpretation are what make the results credible.
How often should outcomes be measured?
At minimum at the start (baseline) and at agreed review points, often aligned with NDIS plan reviews. The cadence should fit the goals and the expected pace of change.
To set meaningful goals and measure outcomes that stand up at plan review, . Speak with Align Network's speech pathology and occupational therapy team.
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