Validation of a fentanyl transdermal adhesion scoring tool for use in clinical practice

Abstract

Context: The therapeutic efficacy of a transdermal system (TDS) is directly related to the adhesion of TDS, with partial adhesion resulting in lower plasma concentration. Currently there is no TDS adhesion scoring tool available for use in the clinical setting.

Objectives: To validate a U.S. Food and Drug Administration (FDA) scoring system for the adhesion of the fentanyl TDS in cancer patients.

Methods: A library of images was created from photographs of fentanyl/placebo TDS placed on patients/volunteers. Thirty photographs, reflecting varying degrees of adhesion, were selected for each of series A and B, with 10 photographs common to both series. Each series was shown to 30 health professionals asked to score the photographs using the FDA scoring system. Validity was assessed using Spearman's rank correlation and reliability by Cohen's kappa (k). Photo editing software was used to assign control scores to each photograph.

Results: Validity was high for both series (≥ 0.954). Inter-reliability (k) ranged from 0.327 to 0.858 (average, 0.547) and 0.433-0.910 (average, 0.620) in series A and B, respectively. The combined agreement across both series was 0.585. Intra-rater agreement (k) of the 10 common images was 0.605. No significant difference was observed between the scoring patterns for those with more than 10 years of working experience.

Conclusion: Overall, the TDS adhesion score determined by the participants visually in this study corresponded well to those generated by photo editing software, thus rendering the scoring system highly valid. The FDA scoring system is an adequate tool for assessing fentanyl TDS adhesion in clinical practice.

Keywords: FDA; TDS adhesion; Transdermal; fentanyl; scoring tool; validation.