Rheumatology The reliability and validation of the EDAQ in RA.pdf (386.69 kB)

The reliability and validity of the English version of the Evaluation of Daily Activity Questionnaire for people with rheumatoid arthritis

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journal contribution
posted on 25.06.2020, 08:46 by Alison Hammond, Yeliz Prior


Objectives. The Evaluation of Daily Activity Questionnaire (EDAQ) includes 138 items in 14 domains

identified as important by people with RA. The aim of this study was to test the validity and reliability

of the English EDAQ.

Methods. A total of 502 participants completed two questionnaires 3 weeks apart. The first consisted of

the EDAQ, HAQ, RA Quality of Life (RAQoL) and the Medical Outcomes Scale (MOS) 36-item Short-Form

Health Survey (SF-36v2), and the second consisted of the EDAQ only. The 14 EDAQ domains were tested

for: unidimensionality—using confirmatory factor analysis; fit, response dependency, invariance across

groups (differential item functioning)—using Rasch analysis; internal consistency [Person Separation

Index (PSI)]; concurrent validity—by correlations with the HAQ, SF-36v2 and RAQoL; and testretest

reliability (Spearman’s correlations).

Results. Confirmatory factor analysis of the 14 EDAQ domains indicated unidimensionality, after adjustment

for local dependency in each domain. All domains achieved a root mean square error of approximation

<0.10 and satisfied Rasch model expectations for local dependency. DIF by age, gender and

employment status was largely absent. The PSI was consistent with individual use (PSI = 0.94 for all

14 domains). For all domains, except Caring, concurrent validity was good: HAQ (rs = 0.720.91),

RAQoL (rs = 0.670.82) and SF36v2 Physical Function scale (rs =0.60 to 0.84) and testretest reliability

was good (rs = 0.700.89).

Conclusion. Analysis supported a 14-domain, two-component structure (Self care and Mobility) of the

EDAQ, where each domain, and both components, satisfied Rasch model requirements, and have robust

reliability and validity.


Arthritis Research UK [project grant no:18497]



University of Salford