Two-dimensional planimetry for alopecia areata severity evaluation compared with severity of alopecia tool: A pilot study

Abstract

Background: Severity of Alopecia Tool (SALT) is widely used to assess the severity of alopecia areata (AA). However, physician-related subjectivity exists in SALT scoring (S1–5), especially with initial inspection in the clinical practice. This study investigated two-dimensional planimetric method to calculate actual surface area of AA, validating SALT scoring. Materials and methods: SALT score was measured twice in each patient based on "initial" inspection in the clinic (SALT-I) and retrospective assessment of the "photograph" (SALT-P). Planimetric surface area was calculated by Image J program. Subgroup analysis was performed depending on the agreement between SALT-I and -P; score was described in the order of SALT-I and SALT-P. Results: A total of 93 subjects were enrolled. Planimetric surface area (cm2) of SALT-I was 2.5–74.9 (S1), 48.8–100.6 (S2), 83.6–205.4 (S3), and 282–367.9 (S4), while SALT-P was 2.5–59.2 (S1), 41.6–205.4 (S2), 48.8–183.2 (S3), and 282–367.9 (S4). In subgroup analysis, SALT-I and SALT-P agreed group showed planimetric surface area (cm2) as 2.5–59.2 (S1-1), 64.2–100.6 (S2-2), 168.3–183 (S3-3), and 282.6–367.9 (S4-4). Disagreed group showed the value as 54.7 (S1-2), 41.6–74.9 (S2-1), 83.6–205.4 (S2-3), and 48.8–88.6 (S3-2). Conclusion: SALT-P was more clearly correlated with actual surface area than SALT-I. Planimetric surface area measurement could be used as a supplementary method especially in the S1 to S3, suggesting 60 cm2, 100 cm2, and 200 cm2 as objective cutoff values to differentiate S1, S2, and S3.