PMID- 17882728
OWN - NLM
STAT- MEDLINE
DCOM- 20080313
LR  - 20191210
IS  - 0963-8288 (Print)
IS  - 0963-8288 (Linking)
VI  - 29
IP  - 20-21
DP  - 2007 Oct 30-Nov 15
TI  - Goal attainment scaling: current methodological challenges.
PG  - 1583-8
AB  - PURPOSE: To validate the underlying mathematical process of Goal Attainment 
      Scaling (GAS), as an illustration of the problems encountered by 
      patient-generated indexes in the quest of patient-centred outcomes. METHODS: Data 
      are simulated to represent the type of input to GAS. Rasch analysis is used to 
      linearize the response categories for each variable associated with each goal, 
      thus making it possible to compare the ordinal non-linear outcome of the GAS 
      process with its linear equivalent, under the assumption of strict 
      unidimensionality. Using a minimum clinically important difference (MCID), the 
      level of difference between the two estimates is assessed. RESULTS: Over 14% of 
      the simulated cases showed a magnitude of difference in change scores between the 
      ordinal and linear-based GAS scores greater than the MCID. These differences were 
      most likely to occur when patients start or finish their GAS scores at the 
      margins of the score range, where non-linearity is greatest. The results show 
      that the GAS process does not support mathematical operations such as 
      multiplication. Apparent clinically meaningful changes scores can be generated 
      solely from the non-linear nature of ordinal scores. CONCLUSIONS: Using 
      patient-centred approaches to measurements such as GAS presents formidable 
      scientific challenges. Suggestions are made which, in the context of GAS 
      applications, may overcome some of these limitations. This involves the 
      establishment of 'item banks' of goals which can be pre-calibrated onto a 
      unidimensional metric such that linearized versions of the various scores (e.g., 
      difficulty) could be imported into the process.
FAU - Tennant, Alan
AU  - Tennant A
AD  - Department of Rehabilitation Medicine, Faculty of Medicine and Health, University 
      of Leeds, UK. a.tennant@leeds.ac.uk
LA  - eng
PT  - Journal Article
PL  - England
TA  - Disabil Rehabil
JT  - Disability and rehabilitation
JID - 9207179
SB  - IM
MH  - Community Health Services
MH  - Disabled Persons/psychology/*rehabilitation
MH  - *Goals
MH  - Health Status
MH  - Humans
MH  - Models, Statistical
MH  - Organizational Objectives
MH  - Outcome Assessment, Health Care/*methods/statistics & numerical data
MH  - *Patient-Centered Care
MH  - Psychometrics/methods
MH  - *Quality of Life
EDAT- 2007/09/21 09:00
MHDA- 2008/03/14 09:00
CRDT- 2007/09/21 09:00
PHST- 2007/09/21 09:00 [pubmed]
PHST- 2008/03/14 09:00 [medline]
PHST- 2007/09/21 09:00 [entrez]
AID - 782121222 [pii]
AID - 10.1080/09638280701618828 [doi]
PST - ppublish
SO  - Disabil Rehabil. 2007 Oct 30-Nov 15;29(20-21):1583-8. doi: 
      10.1080/09638280701618828.