Global Perceived Effect scales provided reliable assessments of health transition in people with musculoskeletal disorders, but ratings are strongly influenced by current status.
OBJECTIVE
The study investigated the test-retest reliability and construct validity of the Global Perceived Effect (GPE) scale in patients with musculoskeletal disorders.


METHODS
Data from seven clinical studies including 861 subjects were used for the analyses. Repeat measures taken at the same attendance and from attendances separated by 24 hours were compared to estimate test-retest reliability. Construct validity was evaluated by examining relationships between pre, post, and change scores in pain and disability measures with GPE measures.


RESULTS
Intraclass correlation coefficient values of 0.90-0.99 indicate excellent reproducibility of the GPE scale. In all but one data set, change scores on pain and disability measures correlated well (r=0.40-0.74) with GPE; however, post scores nearly always correlated even more strongly (r=0.58-0.84), and pre scores showed much weaker association (r=0.00-0.28). Pre scores accounted for only a small amount of additional R(2) when added to regression models including post score.


CONCLUSIONS
Test-retest reliability of the GPE is excellent. GPE ratings are strongly influenced by current status, with the effect more obvious as transition time lengthens. This result questions whether transition ratings truly reflect change, or rather just current state. This finding also has implications for the use of GPE ratings as an external criterion of change in clinimetric studies.
Kamper
Steven J
SJ
The George institute, University of Sydney, PO Box M201 Missenden Rd, Camperdown, NSW 2050, Australia. skamper@george.org.au
Ostelo
Raymond W J G
RW
Knol
Dirk L
DL
Maher
Christopher G
CG
de Vet
Henrica C W
HC
Hancock
Mark J
MJ
D004185:Disability Evaluation; D006305:Health Status Indicators; D019456:Health Transition; D006801:Humans; D009140:Musculoskeletal Diseases / Q000175:diagnosis / Q000453:epidemiology*; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D010146:Pain / Q000175:diagnosis / Q000453:epidemiology*; D015203:Reproducibility of Results