Healthcare & Clinical Formulas
SALT Score (Severity of Alopecia Tool) Weighted Scalp Quadrant Formula
Calculate Elise Olsen’s NAAF Severity of Alopecia Tool score SALT = 0.18*Left + 0.18*Right + 0.40*Top + 0.24*Back (0–100%) and classify JAK-inhibitor trial eligibility (SALT >= 50) vs SALT <= 20 treatment response.
Why top/vertex scalp loss carries 40% of total SALT weight!
Unweighted averages across scalp views distort true hair-loss area because the vertex/top covers more than twice the surface area of either temporal side! Elise A. Olsen and the National Alopecia Areata Foundation (JAAD, 2004) standardized the Severity of Alopecia Tool (SALT, 0–100) by partitioning total scalp surface area into four anatomical quadrants whose weights sum to 1.00: Left Side (18%), Right Side (18%), Top / Vertex (40%), and Back / Occipital (24%), so SALT = 0.18 * L_left + 0.18 * L_right + 0.40 * L_top + 0.24 * L_back!
FDA registrational trials for oral JAK inhibitors (baricitinib BRAVE-AA, ritlecitinib ALLEGRO) define Severe Alopecia Areata entry as SALT >= 50 (>=50% weighted scalp hair loss) and define the primary clinical success endpoint as achieving SALT <= 20! For a patient with Left = 40%, Right = 35%, Top = 65%, and Back = 50% hair loss, weighted SALT = 7.2 + 6.3 + 26.0 + 12.0 = 51.5 (qualifying as Severe S3 >= 50)!
| Weighted SALT Score (0–100) | NAAF Olsen Subclass | Dermatology Trial & Biologic/JAK Milestone |
|---|---|---|
| 0 (No Hair Loss) / 1 – 20 | S0 (0%) / S1 (<=20% Target) | FDA Primary Efficacy Endpoint (SALT <= 20!) |
| 21 – 49 Points | S1 (1–24%) / S2 (25–49%) | Moderate Alopecia Areata |
| 50 – 100 Points (e.g., 51.5 pts) | S3 (50–74%), S4 (75–99%), S5 (100%) | Severe Alopecia Areata (SALT >= 50 Systemic Eligibility) |
Weighted 4-Quadrant SALT Alopecia Score (0–100)
Validates each quadrant hair-loss percentage inside [0, 100] and computes 0.18*B2 + 0.18*B3 + 0.40*B4 + 0.24*B5.
=IF(OR(MIN(B2:B5) < 0, MAX(B2:B5) > 100), "Invalid Quadrant % (0-100)", ROUND(0.18 * B2 + 0.18 * B3 + 0.4 * B4 + 0.24 * B5, 2))SALT Clinical Severity & SALT <= 20 Response Milestone
Flags SALT <= 20 responder milestone, Moderate (20 < SALT < 50), or Severe Alopecia Areata (SALT >= 50).
=IF(OR(MIN(B2:B5) < 0, MAX(B2:B5) > 100), "Invalid Quadrant % (0-100)", IF(0.18 * B2 + 0.18 * B3 + 0.4 * B4 + 0.24 * B5 >= 50, "Severe Alopecia Areata (SALT >= 50)", IF(0.18 * B2 + 0.18 * B3 + 0.4 * B4 + 0.24 * B5 > 20, "Moderate Alopecia Areata (20 < SALT < 50)", "Target Achieved / Mild (SALT <= 20)")))Try the example
Use the original values or change them to test your understanding.