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Revisiting the disabilities of the arm, shoulder and hand (DASH) and QuickDASH in rheumatoid arthritis

Prodinger, B; Hammond, A; Tennant, A; Prior, Y; Tyson, S

Revisiting the disabilities of the arm, shoulder and hand (DASH) and QuickDASH in rheumatoid arthritis Thumbnail


Authors

B Prodinger

A Tennant

S Tyson



Abstract

Background
Limitations in upper limb functioning are common in Musculoskeletal disorders and the Disabilities of the Arm, Shoulder and Hand scale (DASH) has gained widespread use in this context. However, various concerns have been raised about its construct validity and so this study seeks to examine this and other psychometric aspects of both the DASH and QuickDASH from a modern test theory perspective.

Methods
Participants in the study were eligible if they had a confirmed diagnosis of Rheumatoid Arthritis (RA). They were mailed a questionnaire booklet which included the DASH. Construct validity was examined by fit to the Rasch measurement model. The degree of precision of both the DASH and QuickDASH were considered through their Standard Error of Measurement (SEM).

Results
Three hundred and thirty-seven subjects with confirmed RA took part, with a mean age of 62.0 years (SD12.1); 73.6% (n = 252) were female. The median standardized score on the DASH was 33 (IQR 17.5–55.0). Significant misfit of the DASH and QuickDASH was observed but, after accommodating local dependency among items in a two-testlet solution, satisfactory fit was obtained, supporting the unidimensionality of the total sets and the sufficiency of the raw (ordinal or standardized) scores.

Conclusion
Having accommodated local response dependency in the DASH and QuickDASH item sets, their total scores are shown to be valid, given they satisfy the Rasch model assumptions. The Rasch transformation should be used whenever all items are used to calculate a change score, or to apply parametric statistics within an RA population.

Significance and innovations

Most previous modern psychometric analyses of both the DASH and QuickDASH have failed to fully address the effect of a breach of the local independence assumption upon construct validity.

Accommodating this problem by creating ‘super items’ or testlets, removes this effect and shows that both versions of the scale are valid and unidimensional, as applied with a bi-factor equivalent solution to an RA population.

The Standard Error of Measurement of a scale can be biased by failing to take into account the local dependency in the data which inflates reliability and thus making the SEM appear better (i.e. smaller) than the true value without bias.

Citation

Prodinger, B., Hammond, A., Tennant, A., Prior, Y., & Tyson, S. (2019). Revisiting the disabilities of the arm, shoulder and hand (DASH) and QuickDASH in rheumatoid arthritis. BMC Musculoskeletal Disorders, 20(1), 41. https://doi.org/10.1186/s12891-019-2414-6

Journal Article Type Article
Acceptance Date Jan 9, 2019
Online Publication Date Jan 25, 2019
Publication Date Jan 25, 2019
Deposit Date Feb 11, 2019
Publicly Available Date Feb 11, 2019
Journal BMC Musculoskeletal Disorders
Publisher Springer Verlag
Volume 20
Issue 1
Pages 41
DOI https://doi.org/10.1186/s12891-019-2414-6
Publisher URL https://doi.org/10.1186/s12891-019-2414-6
Related Public URLs https://bmcmusculoskeletdisord.biomedcentral.com/

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