The multi-faceted assessment of independence in patients with rheumatoid arthritis: preliminary validation from the ATTAIN study.
OBJECTIVE
To consider the feasibility of assessing multiple facets of independence in rheumatoid arthritis (RA) using a measure developed from existing items and examining its face validity, construct validity and responsiveness to change.


METHODS
The ATTAIN (Abatacept Trial in Treatment of Anti-tumor necrosis factor [TNF] Inadequate responders) database was used. Patients with RA were randomized 2:1, abatacept (n = 258) and placebo (n = 133). A multi-faceted scale to measure physical and psychosocial independence was constructed using items from the Health Assessment Questionnaire (HAQ) and Short Form 36 Health Survey (SF-36). Questions assessing activity limitations and need for outside caregiver help were also examined. Interviews with 20 RA patients assessed face validity.


RESULTS
Item Response Theory analysis yielded two traits - 'Psychosocial Independence', derived from the number of days with activity limitations plus the Role Emotional, Social Functioning and Role Physical subscale items from the SF-36; and 'Physical Independence', derived from 15 HAQ items assessing need for help from another. The two traits showed no significant differential item functioning for age or gender and demonstrated good face validity. Changes over 169 days on Psychosocial Independence were greater (mean 0.46 units, 95% confidence interval [CI]: 0.17-0.75) for the abatacept group than for placebo (p = 0.002). Changes in Physical Independence were greater (mean 0.59 units, 95% CI: 0.35-0.82) for the abatacept group than for placebo (p < 0.001).


CONCLUSIONS
The multi-faceted assessment of independence in RA based on items from commonly used instruments is feasible suggesting promise for evaluating independence in future clinical trials. This approach demonstrated good face and construct validity and responsiveness in RA patients who had previously failed anti-TNF therapy. However, we caution against an interpretation that these data suggest that abatacept improves independence because the component parts of this assessment came from instruments used in the ATTAIN trial where data had been previously analyzed.
Hassett
Afton L
AL
University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick, NJ 08903-0019, USA. a.hassett@umdnj.edu
Li
Tracy
T
Buyske
Steven
S
Savage
Shantal V
SV
Gignac
Monique A M
MA
D000069594:Abatacept; D000203:Activities of Daily Living; D000328:Adult; D000367:Age Factors; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000188:drug therapy* / Q000534:rehabilitation; D004185:Disability Evaluation; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D018796:Immunoconjugates / Q000627:therapeutic use*; D007166:Immunosuppressive Agents / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011379:Prognosis; D011788:Quality of Life; D016059:Range of Motion, Articular / Q000187:drug effects / Q000502:physiology; D018570:Risk Assessment; D012720:Severity of Illness Index; D012737:Sex Factors; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D016896:Treatment Outcome; D054928:Validation Studies as Topic
D018796:Immunoconjugates; D007166:Immunosuppressive Agents; D000069594:Abatacept