Confirmatory factor analysis of the Arthritis Impact Measurement Scales 2 short form in patients with rheumatoid arthritis.
OBJECTIVE
To examine the factorial validity of the short form Arthritis Impact Measurement Scales 2 (AIMS2-SF) in patients with rheumatoid arthritis (RA).


METHODS
Data were from a sample of 279 patients with active RA who completed the long form AIMS2 before starting treatment with tumor necrosis factor alpha-blocking agents. Confirmatory factor analyses were conducted to test and compare the fit of the currently used theoretical measurement model of the AIMS2-SF, originally suggested for the long form AIMS2, and 2 alternative models based on previous exploratory research.


RESULTS
A model with the physical dimension divided into upper and lower body limitations was superior to the current model, and both models provided a clearly better fit than a model without a separate symptom dimension. Under the restrictive assumption of uncorrelated error terms, none of the models achieved a consistent and acceptable fit as judged by several goodness-of-fit indices. Allowing error covariances between 6 pairs of items within the same dimension resulted in an improved and acceptable fit of both the current model and the model with a separate upper and lower body component.


CONCLUSIONS
This study generally supports the factorial validity of the AIMS2-SF and suggests the use of separate scores for upper and lower body limitations. Further research is needed to resolve the issue of high error correlations associated with particular items.
ten Klooster
Peter M
PM
Institute for Behavioral Research, Faculty of Behavioral Sciences, University of Twente, Enschede, The Netherlands. P.M.tenKlooster@utwente.nl
Veehof
Martine M
MM
Taal
Erik
E
van Riel
Piet L C M
PL
van de Laar
Mart A F J
MA
D000328:Adult; D000368:Aged; D018501:Antirheumatic Agents / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010043:Outcome and Process Assessment, Health Care; D015203:Reproducibility of Results; D016896:Treatment Outcome
D018501:Antirheumatic Agents