Field performance of the Skindex-17 quality of life questionnaire: a comparison with the Skindex-29 in a large sample of dermatological outpatients.

The utilization of health-related quality of life (HRQoL) questionnaires in routine clinical practice is hampered by several factors, including their length and thus the time needed to complete and score them. For this reason, growing efforts are devoted both to create short questionnaires and to shorten existing ones. The Skindex-17 is a dermatological HRQoL instrument that was derived from the Skindex-29 using Rasch analysis. It consists of 17 items instead of 29, and answers are given on a three-point scale instead of a five-point scale. The aim of this study was to compare information obtained by the Skindex-29 and the Skindex-17 in a large sample of dermatological outpatients. We compared the Skindex-29 with the Skindex-17 scores in 2,487 patients with several dermatological conditions, using intraclass correlation coefficients. The overall correlation was 0.957 for the symptoms scale and 0.940 for the psychosocial scale. The values were very similar for all diseases. The concordance between the levels of severity of the Skindex subscales in the two instruments was also very high. In conclusion, the Skindex-17 provided very similar information compared with the Skindex-29, with the advantage of being shorter and including some important psychometric properties.