Background: Existing tools for nail psoriasis are complex and may not adequately measure outcomes that are important to patients.
Objectives: We have developed and validated a new tool, the Nail Assessment in Psoriasis and Psoriatic Arthritis (NAPPA), with three components: a questionnaire assessing quality of life (NAPPA-QoL), a two-part questionnaire assessing patient-relevant treatment benefits (the Patient Benefit Index, NAPPA-PBI) and a psoriasis Clinical Assessment of Severity (NAPPA-CLIN).
Methods: Development of the questionnaires involved multiple steps: (i) collection of items about nail psoriasis-related impairments and treatment goals; (ii) selection of 48 items by an expert panel, including patients; (iii) translation into eight languages; (iv) feasibility testing and (v) longitudinal validation in six countries.
Results: Patients found the questionnaires clear (84%) and comprehensible (95%). NAPPA-QoL and NAPPA-PBI scores correlated moderately with clinical outcomes [e.g. Nail Psoriasis Severity Index (NAPSI)] and markedly with other quality-of-life questionnaires (e.g. EQ-5D™). Both questionnaires were sensitive to change. Internal consistency was good (Cronbach α ≥ 0.88 for all scales). The NAPPA-CLIN, a brief version of NAPSI that involves assessment of only four digits rather than all 20, was found to correlate highly with total NAPSI score (r = 0.97, P < 0.001).
Conclusions: Overall, the three-component NAPPA tool is a valid, reliable and practical instrument to assess patient-relevant nail psoriasis outcomes.
© 2013 British Association of Dermatologists.