NAPSI Calculator

Nail Psoriasis Severity Index — Rich & Scher, 2003

Purpose
Numeric, reproducible grading of nail psoriasis severity, scoring nail matrix and nail bed signs by quadrant in each nail.
Population
Patients with psoriatic nail involvement (plaque psoriasis or psoriatic arthritis). Used as outcome in clinical trials; may be applied to all 20 nails, to fingernails only, or to a single target nail.
Formula
Per nail: matrix score (0–4, number of quadrants with any matrix sign) + bed score (0–4, number of quadrants with any bed sign) = 0–8 · Total 0–80 (10 fingernails) or 0–160 (20 nails)
Severity thresholds
No validated severity cut-offs have been published. Trials report change from baseline (e.g. NAPSI 50/75). Higher score = more severe nail disease.
🔍 Signs to assess

Divide each nail into four quadrants with imaginary horizontal and vertical lines. For each nail, count the number of quadrants (0–4) showing any nail matrix sign, and the number of quadrants (0–4) showing any nail bed sign. Each nail scores 0–8.

Nail matrix psoriasis (0–4) Pitting · Leukonychia · Red spots in the lunula · Crumbling
Nail bed psoriasis (0–4) Onycholysis · Splinter haemorrhages · Oil-drop (salmon patch) discoloration · Subungual hyperkeratosis

Use the switch on each nail to exclude nails that cannot be assessed (absent, traumatic or onychomycotic nails). The maximum score adjusts automatically.

🖐️ Fingernails
 · 
Fingernail NAPSI 0 / 80
📚 References
  1. Rich P, Scher RK. Nail Psoriasis Severity Index: a useful tool for evaluation of nail psoriasis. J Am Acad Dermatol. 2003;49(2):206–12.
  2. Cassell SE, Bieber JD, Rich P, et al. The modified Nail Psoriasis Severity Index: validation of an instrument to assess psoriatic nail involvement in patients with psoriatic arthritis. J Rheumatol. 2007;34(1):123–9.
  3. Rigopoulos D, Baran R, Chiheb S, et al. Recommendations for the definition, evaluation, and treatment of nail psoriasis in adult patients with no or mild skin psoriasis: a dermatologist and nail expert group consensus. J Am Acad Dermatol. 2019;81(1):228–40.
  4. Nast A, Smith C, Spuls PI, et al. EuroGuiDerm Guideline on the systemic treatment of psoriasis vulgaris — Part 2: specific clinical and comorbid situations. J Eur Acad Dermatol Venereol. 2021;35(2):281–317.
Clinical decision support only. This tool is intended to assist clinical assessment and does not replace professional judgment. Always interpret results in the context of the individual patient.