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

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 (cm(2)) 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 (cm(2)) 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 cm(2), 100 cm(2), and 200 cm(2) as objective cutoff values to differentiate S1, S2, and S3.