Quality of life in neurofibromatosis 1: development and validation of a tool dedicated to cutaneous neurofibromas in adults.

Background: Cutaneous neurofibromas (cNF), present in 95% of individuals with neurofibromatosis 1 (NF1), are considered as one of the greatest medical burden because of physical disfigurement. No specific score evaluates their impact on quality of life (QoL).

Objective: To develop a specific score assessing cNF-related QoL.

Methods: Through a multidisciplinary workshop including 10 patients, 3 expert-in-NF1 physicians, 3 health care workers (nurses and psychologist) and 1 methodologist, the French version of the Skindex-16 was modified by adding 3 items. The new cNF-Skindex was validated among patients with NF1 recruited in the ComPaRe online cohort, in France (N = 284). Construct validity was assessed by comparing it with the EQ-5D-5L, its visual analogue scale and the MYMOP2 and by assessing its association with patients' characteristics. Reliability was assessed by a test-retest. An English version of the tool was developed using a back-forward translation.

Results: A total of 228 individuals with NF1, with cNF answered the 19-item questionnaire. These items fitted into 3 domains: emotions, symptoms, functioning. One was dropped during analysis because >90% responders were not concerned. The cNF-Skindex significantly correlated with the EQ-5D-5L (N = 193) and MYMOP2 (N = 210) indicating good external validity: rs 0.38 (P < 0.001), and 0.58 (P < 0.001), respectively. Having >50 cNF was the only independent variable associated with the total score cNF-Skindex (β = 15.88, 95%CI 6.96-24.81, P = 0.001), and with the 3 sub-scores: 'functioning' (β = 2.65, 95%CI 0.71-4.59, P = 0.008), 'emotions' (β = 17.03, 95%CI 4.11-29.96, P = 0.010) and 'symptoms' (β = 3.90, 95%CI 1.95-5.85, P < 0.001). Test-retest reliability (N = 133) found an ICC at 0.96 demonstrating good reproducibility.

Conclusion: The cNF-Skindex demonstrated excellent psychometric properties. The global and sub-scores were increased with higher number of cNF arguing for its use in further trials aiming to reduce their number or prevent their development. Cross-cultural validation and evaluation of its responsiveness are the next steps.