Goal Attainment Scaling in paediatric rehabilitation practice: a useful outcome measure

Abstract

The main aim of this thesis was to investigate the use of a 6-point Goal Attainment Scaling (GAS) system to measure change over time in interdisciplinary rehabilitation practice for children with Cerebral Palsy (CP). GAS is a generic individualized evaluative criterion-referenced instrument. It can be used for measurement of changes in activities and participation in individual patients and in groups of patients. First a study to measure the effect of Botulinum Toxin A treatment was performed using GAS. A single-blind randomized multiple baseline/treatment phase study across subjects was used for 33 goals of 11 children with CP. Each goal was recorded weekly with a standard video for a period of 14 weeks. Rating of pre-determined GAS scales was performed blinded. This study showed that GAS could demonstrate clinically relevant improvement in individual rehabilitation goals. Second, a critical review of the literature about the content reliability, inter-rater reliability, validity, sensitivity to change of GAS and its use in paediatric rehabilitation research was performed. The review showed that current knowledge about its reliability, when used with children, was insufficient. Moreover, its added value and responsiveness should be explored more specifically. This resulted in the next project which was performed on the clinimetric properties of GAS. We started by developing a training program for physical, occupational, speech-language therapists, paediatric psychologists and social workers. We determined criteria for GAS scales: they should be ordinal, describe specific, measurable, acceptable, realistic abilities, activities or participation in a single dimension, use the ‘can-do’ principle and it should be possible to score them within 10 minutes. Therapists and parents regarded GAS as a suitable tool to improve the quality of rehabilitation treatment. The first issue we investigated was the inter-rater reliability. A reliability study was performed in which 23 children with CP and 20 trained therapists of 3 disciplines were enrolled. The child’s own therapists, and for each therapist an independent therapist from the same discipline, constructed 64 GAS scales each. They scored both their own scale and their partner’s scale resulting in 128 scores. The inter-rater reliability of GAS was good. The results also suggested that scale construction by the child’s own therapist as opposed to an independent rater has a positive influence on the inter-rater reliability of the scales. This finding was reassuring regarding the phenomenon of “therapist bias”. Finally, the content of GAS scales was compared to the PEDI and GMFM-66 using the ICF-CY. The instruments were complementary in construct and individual responsiveness. A substantial number of achieved goals could have been missed if only standardized measures were used, even if the ICF-item of the rehabilitation goal matched the items of these measures. Moreover, by using GAS alone, small changes could have been missed. Positive attributes of GAS include quantifying the relevance of the change measured, the comparability of goal attainment across goals and individuals, and the ability to measure progress that would otherwise not have been measured. Issues regarding GAS include reservations about the content validity related to the professional insight.