Study design: Retrospective cohort BACKGROUND: Exploratory Factor Analysis (EFA) and structural equation modelling (SEM) assess relationships between questionnaire items and the constructs ("factors") measured by a questionnaire. The QuickDASH has not been subjected to these analyses in Dupuytren's disease.
Purpose: To undertake EFA and SEM to identify the factors measured by the QuickDASH in patients with Dupuytren's disease.
Methods: We identified 750 cases of surgery for Dupuytren's disease at a single center with preoperative QuickDASH scores. We performed EFA on QuickDASH responses in R, using established methodology. Based on the EFA results, we conducted SEM in a training sample of 200 participants. A test SEM analysis was performed in a second, independent sample of 200 participants.
Results: EFA suggested a 2-factor model. Items 1-6 measured one factor (we interpreted this as "hand function"), whereas items 9-11 measured a different factor ("hand symptoms"). Items 7 and 8 (social and work activities) did not reflect either of these factors well, and may be influenced by other variables. A structural equation model based on the EFA results, with 2 first-order factors, demonstrated excellent fit in our first SEM sample. This was confirmed with a second independent sample in a test analysis.
Conclusions: The QuickDASH PROM may measure 2 distinct factors in patients with Dupuytren's disease. This aligns with previous analyses of the full-length DASH PROM. Separation of the QuickDASH PROM into 2 sub-scales with distinct scores to measure "hand function" and "hand symptoms" may improve its structural validity in patients with Dupuytren's disease.
Keywords: Dupuytren's disease; Factor analysis; PROMs; Psychometric analysis.
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