Validating and assessing the sensitivity of the Health Assessment Questionnaire-Disability Index-derived Short Form-6D in patients with early aggressive rheumatoid arthritis.
OBJECTIVE
New methodologies allow the scores for the Health Assessment Questionnaire-Disability Index (HAQ-DI) to be translated into preferences/utility scores. We evaluated the construct validity of the HAQ-DI-derived Short Form-6D (SF-6D) score and assessed its responsiveness to change over 6- and 12-month followup periods in patients with early aggressive rheumatoid arthritis (RA).


METHODS
Patients (n=277) participating in an RA observational study completed self-reported measures of symptoms and the HAQ-DI at baseline and at 6 and 12 months. Total Sharp scores, C-reactive protein, and erythrocyte sedimentation rate were assessed along with clinical data. Construct validity was assessed by examining the association between SF-6D score and patient-reported and clinical measures using Spearman correlation coefficients. The responsiveness of SF-6D to change was assessed using patient and physician assessments of the disease as clinical anchors. The magnitude of responsiveness was calculated using SF-6D effect size (ES).


RESULTS
Mean SF-6D scores were 0.690, 0.720, and 0.723 at baseline and 6 and 12-month followup, respectively. Baseline patient-reported measures had moderate to high correlations with baseline SF-6D (r=0.43 to 0.52); whereas clinical measures had negligible to low correlations with SF-6D (r=0.001 to 0.32). ES was moderate for the groups that were deemed to have improved (ES 0.63-0.75) but negligible to small for those that did not (ES 0.13-0.46).


CONCLUSIONS
Our data support the validity and responsiveness of the HAQ-DI derived SF-6D score in an early RA cohort. These results support the use of the HAQ-DI derived SF-6D in RA cohorts and clinical trials lacking preference-based measures.
Division of Rheumatology, University of California Los Angeles School of Medicine, Department of Health Services, 1000 Veteran Avenue, Room 32-59, Rehabilitation Center, Los Angeles, CA 90095, USA.
Sogol S
SS
Amjadi
Paul M
PM
Maranian
Harold E
HE
Paulus
Robert M
RM
Kaplan
Veena K
VK
Ranganath
Daniel E
DE
Furst
Puja P
PP
Khanna
Dinesh
D
Khanna
D001172:Arthritis, Rheumatoid / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D004185:Disability Evaluation; D005221:Fatigue / Q000150:complications / Q000503:physiopathology; D005260:Female; D006304:Health Status; D006801:Humans; D007256:Information Systems; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010146:Pain / Q000150:complications / Q000503:physiopathology; D010147:Pain Measurement; D011237:Predictive Value of Tests; D011788:Quality of Life; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*