Comparison of the paper-based and electronic versions of the Dermatology Life Quality Index (DLQI): evidence of equivalence

Abstract

Background

The use of patient-reported outcome measures in electronic format has been increasing. However, these formats are usually not validated or compared to the original paper-based formats, so there is no evidence that they are completed in the same way.

Objectives

The aim of this study was to compare the conventional paper version and a web-based application version (iPad^®) of the DLQI to assess equivalence of scores.

Methods

The study employed a randomized cross-over design using a within-subjects comparison of the two formats of the questionnaire. International Society for Pharmacoeconomics and Outcomes Research (ISPOR) guidelines were followed. Subjects aged over 18 years with any confirmed skin condition were recruited from a teaching hospital dermatology outpatient clinic. Expected Intra-class correlation coefficient (ICC) was 0.9 (α = 0.05)

Results

A total of 104 patients were recruited, median age=53.5 years (IQR=37.3-67.8, 43% male). The Intraclass correlation coefficient (ICC) showed high concordance between the total DLQI scores from paper and iPad^® versions (ICC = 0.98; 95% CI 0.97-0.99). Patients took a median of 78 seconds to complete the electronic version and 73 seconds for paper (p=0.008): 76% preferred the electronic version and perceived completion to take a shorter time.

Conclusions

There is high concordance, and thus equivalence, between the iPad and paper versions of the DLQI, with an ICC of 0.98, and a clear patient preference for the iPad version.

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