Development and Validation of a Patient-Reported Outcome Measure for Fingernail and Toenail Conditions: The NAIL-Q

Area of Science:

• Dermatology
• Psychometrics
• Health Outcomes Research

Background:

• Patient-reported outcome measures (PROMs) are essential for capturing outcomes that matter to patients with nail conditions.
• Existing PROMs may not adequately address the unique concerns associated with toenail and fingernail conditions.

Purpose of the Study:

• To design and validate a comprehensive new PROM, termed NAIL-Q, for assessing outcomes in patients with nail conditions.
• To ensure the NAIL-Q measures aspects of nail health, appearance, and treatment outcomes from the patient's perspective.

Main Methods:

• A mixed-methods iterative approach was employed, including concept elicitation interviews, cognitive debriefing, and expert input.
• Data were collected from an international sample via crowdsourcing, with subsequent psychometric evaluation using Rasch Measurement Theory (RMT).
• Psychometric testing included assessment of item and scale performance, test-retest reliability, and convergent and construct validity.

Main Results:

• The NAIL-Q was developed with 45 items across 7 scales measuring nail appearance, quality of life, and treatment outcomes.
• Rasch Measurement Theory analysis confirmed good item and scale performance, with high reliability (Person Separation Index ≥0.79, Cronbach's alpha ≥0.83) and reliability (intraclass correlation coefficients ≥0.81).
• The NAIL-Q demonstrated strong construct validity, with participants finding it easy to understand, relevant, and respectful, supporting its use in clinical care.

Conclusions:

• The NAIL-Q is a rigorously developed and validated PROM for assessing nail appearance, health-related quality of life, and treatment outcomes.
• This PROM can be effectively utilized in clinical practice to guide patient care.
• The NAIL-Q facilitates the inclusion of the patient perspective in research related to nail conditions.