Validated, Reliable, and Novel Skin Frailty Scale for Outpatient Usage and Its Association With Age, Sex, and Non‐Melanoma Skin Cancer: An Observational Study

ABSTRACT Background Age‐associated skin frailty affects hundreds of millions of adults globally. However, a validated and reliable scale to visually quantitate skin frailty is lacking, posing a barrier to clinical care and research. Objectives To develop a validated and reliable visual scale for skin frailty and assess its association with demographic and clinical factors. Methods Stanford Human Subjects Panel approval and informed consent were obtained prior to all procedures. Skin frailty parameters were identified on a literature review and assessed by two expert board‐certified dermatologists to generate content validity indices (CVIs). Skin frailty parameters on 219 digital photographs of the upper extremity in outpatient adult volunteers (age 18–89 years) were assessed, with reliability calculated by Kendall's coefficient or Gwet's AC2. A Skin Frailty Score (SFS) was developed using parameters with excellent, good, or moderate reliability. SFS was interrogated for the association with demographic/clinical factors. To improve SFS usability, factor analysis was performed to reduce the number of parameters, while retaining reliability and clinical relevance. Results Nine parameters demonstrated CVI > 0.80. Strong intra‐rater reliability was observed for these 9 parameters (Kendall's coefficient or Gwet's AC2 > 0.80). Strong inter‐rater reliability was observed for 8/9 parameters (Kendall's coefficient and Gwet's AC2 > 0.80); one showed good inter‐rater reliability (Kendall's coefficient = 0.67). This 9‐parameter SFS demonstrated good intra‐rater reliability (intra‐class correlation coefficient = 0.85) and moderate inter‐rater reliability (intra‐class correlation coefficient = 0.69). By multivariate analysis, higher SFS was associated with age, female sex, and non‐melanoma skin cancer (all p < 0.01). To improve SFS usability, factor analysis enabled parameter reduction to 6, while maintaining moderate inter‐rater and good intra‐rater reliability (intra‐class correlation coefficient = 0.62 and 0.77, respectively) and clinical relevance. Conclusions SFS is a novel, validated, and reliable visual scoring scale of skin frailty of the upper extremity that could be incorporated into clinical and research settings.