QuickDASH questionnaire items behave as 2 distinct subscales rather than one scale in Dupuytren's disease

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.

To undertake EFA and SEM to identify the factors measured by the QuickDASH in patients with Dupuytren's disease.

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.

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.

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.