Nail Psoriasis and Quality-of-Life Measurement in Clinical Trials: Call for the Use of Nail-Specific Instruments.

Nail involvement is frequent in people with psoriasis. It can considerably impair health-related quality of life (HRQoL) beyond the impairments due to other psoriasis symptoms, for example, because patients feel ashamed of visible nail defects or because of the functional impairment in manual activities and walking. In clinical trials on nail psoriasis, it is therefore crucial to assess whether the treatment reduces HRQoL impairments that are specific to nail psoriasis. For this purpose, two validated patient questionnaires are available, the Nail Psoriasis Quality of Life Scale (NPQ10) and the Nail Assessment in Psoriasis and Psoriatic Arthritis-Quality of Life (NAPPA-QOL). The ten-item NPQ10 has the advantage of being short and thus quick to administer. The 20-item NAPPA-QOL, in contrast, assesses the different dimensions of HRQoL which is considered a multi-dimensional construct. Yet most randomized controlled trials on nail psoriasis do not evaluate HRQoL improvement. If they do, a number of different instruments are used, most of which are not nail specific. This makes comparison of trial outcomes difficult. Harmonizing the measurement of HRQoL in future clinical trials on nail psoriasis would improve comparability across studies and would also enhance the reliability of meta-analyses.