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.
Keywords: alopecia; alopecia areata; severity of alopecia tool; severity of illness index.
© 2023 The Authors. Skin Research and Technology published by John Wiley & Sons Ltd.