Ichthyosis Scoring System Reliable in Measuring Global Ichthyosis Severity

Prior to the ISS, there was no known scale to measure ichthyosis severity across the entire body.

A new qualitative study found that a comprehensive scoring system called the Ichthyosis Scoring System (ISS) was reliable in measuring global ichthyosis severity in adults and children.

Investigators noted that qualitative grading of ichthyosis is crucial to helping dermatologists determine appropriate treatments in clinical practice, with multiple randomized clinical trials requiring reliable assessments of ichthyosis severity to identify appropriate participants to receive therapy and quantify treatment outcomes.

There is no known scale to measure ichthyosis severity across the entire body, and only 2 visual ichthyosis scales have undergone rigorous evaluation, including Visual Index for Ichthyosis Severity (VIIS) and the Ichthyosis Area Severity Index (IASI). However, many of these instruments do not focus on body sites of functional and psychosocial significance for patients.

As such, investigators led by Qisi Sun, MD, Department of Dermatology, Pathology, and Genetics at Yale University School of Medicine, reported on the development and initial validation of the ISS.

The Methods

The team utilized 2 ichthyosis experts who led central efforts to define ISS content, while members of the Foundation for Ichthyosis and Relates Skin Types Medical and Scientific Advisory Board provided further input.

Written informed consent and assent were obtained from all participants 7 years and older and from patients for children younger than 18 years.

The ISS captured information at 10 body regions in scalp, face, neck, torso, elbows, palms, upper extremities, knees, soles, and lower extremities.

From there, each body site was assessed separately for including scale and erythema, 2 characteristics most shared among congenital ichthyoses.

Photographic standards were taken from the National Registry of Ichthyosis and Related Disorders data set for scale and erythema that represented all severity levels, which resulted in an 83-image teaching set.

After creating photographic standards, the team created written standard descriptions representing each severity level for scale and erythema.

Participants of all ages, races, and ethnicities were included in the creation of ISS, and dermatologists with varying experience and areas of expertise participated as raters to evaluate it.

The Findings

Investigators believed the ISS capitalized on the strengths of VIIS and IASI by including detailed descriptors adapted from the VIIS while leveraging the comprehensive assessment of IASI.

Across both cohorts of 11 dermatologists in total, the intraclass correlation coefficients for total, scale and erythema scores were greater than 0.90 (95% CI, 0.77-0.97), greater than 0.91 (95% CI, 0.79-0.98), and greater than 0.88 (95% CI, 0.72-0.97), respectively.

Investigators also observed that most body sites exhibited moderate to good interrater reliabilities for scale and erythema.

Among physicians, the ISS demonstrated excellent agreement, which investigators deemed notable given the heterogeneity of participants analyzed.

“The robust overall interrater and interrater reliabilities, coupled with the scale’s ease of use and content validity, suggest that the ISS may be used with accuracy in clinical as well as research settings and potentially adopted globally as the criterion standard ichthyosis severity index,” the team said.

The study, "Development and Initial Validation of a Novel System to Assess Ichthyosis Severity," was published online in JAMA Dermatology.