Background: A software program called "HOYS" has been developed to depict various aspects and degrees of aging at 35 constituent subregions of seven distinct facial or exposed extrafacial regions. This program is underpinned by five-point photonumeric Likert scales characterizing skin surface and volume changes across five decades for each of the 35 subregions, and features an interactive skin-age assessment with a treatment-prioritization tool. In this study, the reliability and reproducibility of these scales was evaluated.
Methods: Eleven physicians and 19 non-physicians participated in this study. The five images from each of the 35 Likert scales in the HOYS program were shown on a total of 43 display boards, with selected subregions presented at rest or with movement, consistent with this program. Each image was randomly labeled between "A-E," corresponding to a range of skin ages by decade from 20-69 years. Each rater was asked to rank these images from youngest to oldest (or least to most severe deficit) for each scale and to repeat this exercise 2 hours later, with the intra- and inter-rater reliability evaluated. The raters were also asked to estimate the age of a single randomly allocated image on each scale for the purposes of internal validation.
Results: The overall inter-rater reliability of the raters was high at the first ranking session (weighted kappa: 0.78; 95% confidence intervals [95% CI]: 0.77-0.79) and this was confirmed when repeated 2 hours later (0.82; 95% CI: 0.81-0.83), with an intra-rater reliability of 0.76 (95% CI: 0.75-0.77). There was no significant difference in the physicians' and non-physicians' rankings. The raters also accurately estimated the actual age of the single randomly allocated image from each of the 43 stations (0.72; 95% CI: 0.70-0.74). A very similar pattern was observed when the ratings of a constituent of one of the seven regions, the perioral/lower face, were analyzed for expounding purposes.
Conclusion: The high reliability and reproducibility of the ranking in this validation study suggests that the five-point photonumeric Likert scales used in the HOYS program are an accurate depiction of age-related changes over five decades in the seven facial and extrafacial regions represented in this program, from the ages of 20-69 years.
Keywords: HOYS; age-related skin changes; inter-rater; intra-rater; photonumeric scale; reliability; validation.