Single-factor scoring validation for the Health Assessment Questionnaire-Disability Index (HAQ-DI) in patients with systemic sclerosis and comparison with early rheumatoid arthritis patients.
OBJECTIVE
Structural validity for the Health Assessment Questionnaire-Disability Index (HAQ-DI) has recently been provided for patients with rheumatoid arthritis (RA). The goal of the current study was to examine the structural validity of the HAQ-DI in patients with systemic sclerosis (SSc, scleroderma) and to compare its performance with that in patients with RA.


METHODS
The HAQ-DI structural validity was first assessed in a sample of 100 scleroderma patients using confirmatory factor analysis. Second, the similarity of factor structures between SSc patients (n = 291) and RA patients (n = 278) was tested using a multigroup structural validity model to assure that comparison of scores between these two diagnostic groups is appropriate.


RESULTS
Results yielded a single-factor HAQ-DI score which favored the current scoring system of the HAQ-DI (model fit was CFI = 0.99 and RMSEA = 0.04). Moreover, even the most stringent model of multigroup structural validity affirmed the similarity between SSc and RA patients on the HAQ-DI (model fit was CFI = 0.99 and RMSEA = 0.04) nor was it different from a model without any demands on group similarity: CFI difference = 0.007; chi(2) = 4.29, df = 26, p=0.99.


CONCLUSIONS
The current results indicate that a single-factor HAQ-DI is appropriate for future clinical trials in scleroderma and, in addition, HAQ-DI scores among patients with SSc and early RA can be compared legitimately with one another.
Cole
Jason C
JC
Consulting Measurement Group, Huntington Beach, CA 91403, USA. jcole@webcmg.com
Khanna
Dinesh
D
Clements
Philip J
PJ
Seibold
James R
JR
Tashkin
Donald P
DP
Paulus
Harold E
HE
Irwin
Michael R
MR
Motivala
Sarosh J
SJ
Furst
Daniel E
DE
D000203:Activities of Daily Living; D001172:Arthritis, Rheumatoid / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D015337:Multicenter Studies as Topic; D011594:Psychometrics / Q000295:instrumentation*; D016032:Randomized Controlled Trials as Topic; D012595:Scleroderma, Systemic / Q000503:physiopathology*; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D014481:United States