Emergency · LIVE

Psoriasis Area and Severity Index (PASI)

PASI

Compute Fredriksson 1978 PASI from four body regions. For each region the caller assigns area 0-6 and three intensity signs (erythema, induration, scaling) each 0-4. Region score = (sum of 3 signs) × area × adult weight. Total PASI is the sum (max 72).

LIVE $0.005 USDC GET /api/calc/pasi

Markdown: /docs/pasi.md · Canonical: https://magentlab.com/docs/pasi

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Compute Fredriksson 1978 PASI from four body regions. For each region the caller assigns area 0-6 and three intensity signs (erythema, induration, scaling) each 0-4. Region score = (sum of 3 signs) × area × adult weight. Total PASI is the sum (max 72).

When to use

When an agent already has caller-assigned Fredriksson 1978 PASI region area and sign integers and needs the published adult-weight total. magent does not examine the skin, diagnose psoriasis, apply pediatric region weights, or assign Investigator Global Assessment or later mild-moderate-severe PASI cutoffs. Not EASI (EASI uses four signs 0-3 including edema).

When not to use

• Not a medical device and not a diagnosis of psoriasis or a treatment order. magent does not examine the skin. Each area (0-6) and sign (0-4) is a caller-assigned integer.
• magent uses the published adult area weights (head 0.1, upper extremities 0.2, trunk 0.3, lower extremities 0.4). It does not apply later pediatric head 0.2 and lower-extremity 0.3 multipliers.
• Fredriksson 1978 published no Investigator Global Assessment or mild-moderate-severe PASI cutoffs. magent returns the numeric PASI only.
• Each sign is a caller-assigned integer 0-4 (0 none, 1 slight, 2 moderate, 3 severe, 4 very severe). magent does not accept half-point grades. PASI uses three signs, not EASI's four signs 0-3 including edema.

Formula

PASI = 0.1*(head_erythema + head_induration + head_scaling)*head_area + 0.2*(upper_extremities_erythema + upper_extremities_induration + upper_extremities_scaling)*upper_extremities_area + 0.3*(trunk_erythema + trunk_induration + trunk_scaling)*trunk_area + 0.4*(lower_extremities_erythema + lower_extremities_induration + lower_extremities_scaling)*lower_extremities_area; each area integer 0-6 (0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%); each of erythema, induration, and scaling integer 0-4 (0 none, 1 slight, 2 moderate, 3 severe, 4 very severe); adult region weights head 0.1, upper extremities 0.2, trunk 0.3, lower extremities 0.4; max 72; magent uses these adult weights only; this paper published no Investigator Global Assessment or mild-moderate-severe PASI cutoffs

Citation

Title

Severe psoriasis--oral therapy with a new retinoid

Authors

Fredriksson T, Pettersson U

Source

Dermatologica. 1978;157(4):238-244

DOI

10.1159/000250839

Worked example

Also searched as

• PASI
• Psoriasis Area and Severity Index
• Fredriksson PASI
• PASI score
• psoriasis severity index
• Fredriksson 1978 PASI
• psoriasis area severity
• PASI 72

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/pasi?head_area=0&head_erythema=0&head_induration=0&head_scaling=0&upper_extremities_area=0&upper_extremities_erythema=0&upper_extremities_induration=0&upper_extremities_scaling=0&trunk_area=0&trunk_erythema=0&trunk_induration=0&trunk_scaling=0&lower_extremities_area=0&lower_extremities_erythema=0&lower_extremities_induration=0&lower_extremities_scaling=0

Full URL: https://api.magentlab.com/api/calc/pasi?head_area=0&head_erythema=0&head_induration=0&head_scaling=0&upper_extremities_area=0&upper_extremities_erythema=0&upper_extremities_induration=0&upper_extremities_scaling=0&trunk_area=0&trunk_erythema=0&trunk_induration=0&trunk_scaling=0&lower_extremities_area=0&lower_extremities_erythema=0&lower_extremities_induration=0&lower_extremities_scaling=0

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/pasi?head_area=0&head_erythema=0&head_induration=0&head_scaling=0&upper_extremities_area=0&upper_extremities_erythema=0&upper_extremities_induration=0&upper_extremities_scaling=0&trunk_area=0&trunk_erythema=0&trunk_induration=0&trunk_scaling=0&lower_extremities_area=0&lower_extremities_erythema=0&lower_extremities_induration=0&lower_extremities_scaling=0"

Parameters

Bulk (POST)

POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement.

POST /api/calc/pasi Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 PREVIEW

• 1 to 25 items. Each item uses the same keys as the GET query parameters.
• POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows.
• The first invalid item fails the whole request (index in the 400 JSON). You are not charged.
• HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row.
• Catalog misses (empty matches, found=false) stay paid 200s inside that slot.
• x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items.

Example request (fixture)

{
  "items": [
    {
      "head_area": "0",
      "head_erythema": "0",
      "head_induration": "0",
      "head_scaling": "0",
      "lower_extremities_area": "0",
      "lower_extremities_erythema": "0",
      "lower_extremities_induration": "0",
      "lower_extremities_scaling": "0",
      "trunk_area": "0",
      "trunk_erythema": "0",
      "trunk_induration": "0",
      "trunk_scaling": "0",
      "upper_extremities_area": "0",
      "upper_extremities_erythema": "0",
      "upper_extremities_induration": "0",
      "upper_extremities_scaling": "0"
    },
    {
      "head_area": "0",
      "head_erythema": "0",
      "head_induration": "0",
      "head_scaling": "0",
      "lower_extremities_area": "0",
      "lower_extremities_erythema": "0",
      "lower_extremities_induration": "0",
      "lower_extremities_scaling": "0",
      "trunk_area": "0",
      "trunk_erythema": "0",
      "trunk_induration": "0",
      "trunk_scaling": "0",
      "upper_extremities_area": "0",
      "upper_extremities_erythema": "0",
      "upper_extremities_induration": "0",
      "upper_extremities_scaling": "0"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/pasi",
  "items": [
    {
      "components": [
        {
          "value": 0,
          "factor": "head",
          "weight": 0.1,
          "points": 0.0,
          "present": true,
          "area": 0
        },
        {
          "value": 0,
          "factor": "upper_extremities",
          "weight": 0.2,
          "points": 0.0,
          "present": true,
          "area": 0
        },
        {
          "value": 0,
          "factor": "trunk",
          "weight": 0.3,
          "points": 0.0,
          "present": true,
          "area": 0
        },
        {
          "value": 0,
          "factor": "lower_extremities",
          "weight": 0.4,
          "points": 0.0,
          "present": true,
          "area": 0
        }
      ],
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Fredriksson T, Pettersson U",
        "doi": "10.1159/000250839",
        "id": "fredriksson-1978",
        "pmid": "357213",
        "source": "Dermatologica. 1978;157(4):238-244",
        "title": "Severe psoriasis--oral therapy with a new retinoid"
      },
      "formula": "pasi",
      "formula_expression": "PASI = 0.1*(head_erythema + head_induration + head_scaling)*head_area + 0.2*(upper_extremities_erythema + upper_extremities_induration + upper_extremities_scaling)*upper_extremities_area + 0.3*(trunk_erythema + trunk_induration + trunk_scaling)*trunk_area + 0.4*(lower_extremities_erythema + lower_extremities_induration + lower_extremities_scaling)*lower_extremities_area; each area integer 0-6 (0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%); each of erythema, induration, and scaling integer 0-4 (0 none, 1 slight, 2 moderate, 3 severe, 4 very severe); adult region weights head 0.1, upper extremities 0.2, trunk 0.3, lower extremities 0.4; max 72; magent uses these adult weights only; this paper published no Investigator Global Assessment or mild-moderate-severe PASI cutoffs",
      "max_score": 72,
      "score": 0.0,
      "lower_extremities_score": 0.0,
      "trunk_score": 0.0,
      "upper_extremities_score": 0.0,
      "head_score": 0.0
    },
    {
      "components": [
        {
          "value": 0,
          "factor": "head",
          "weight": 0.1,
          "points": 0.0,
          "present": true,
          "area": 0
        },
        {
          "value": 0,
          "factor": "upper_extremities",
          "weight": 0.2,
          "points": 0.0,
          "present": true,
          "area": 0
        },
        {
          "value": 0,
          "factor": "trunk",
          "weight": 0.3,
          "points": 0.0,
          "present": true,
          "area": 0
        },
        {
          "value": 0,
          "factor": "lower_extremities",
          "weight": 0.4,
          "points": 0.0,
          "present": true,
          "area": 0
        }
      ],
      "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Fredriksson T, Pettersson U",
        "doi": "10.1159/000250839",
        "id": "fredriksson-1978",
        "pmid": "357213",
        "source": "Dermatologica. 1978;157(4):238-244",
        "title": "Severe psoriasis--oral therapy with a new retinoid"
      },
      "formula": "pasi",
      "formula_expression": "PASI = 0.1*(head_erythema + head_induration + head_scaling)*head_area + 0.2*(upper_extremities_erythema + upper_extremities_induration + upper_extremities_scaling)*upper_extremities_area + 0.3*(trunk_erythema + trunk_induration + trunk_scaling)*trunk_area + 0.4*(lower_extremities_erythema + lower_extremities_induration + lower_extremities_scaling)*lower_extremities_area; each area integer 0-6 (0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%); each of erythema, induration, and scaling integer 0-4 (0 none, 1 slight, 2 moderate, 3 severe, 4 very severe); adult region weights head 0.1, upper extremities 0.2, trunk 0.3, lower extremities 0.4; max 72; magent uses these adult weights only; this paper published no Investigator Global Assessment or mild-moderate-severe PASI cutoffs",
      "max_score": 72,
      "score": 0.0,
      "lower_extremities_score": 0.0,
      "trunk_score": 0.0,
      "upper_extremities_score": 0.0,
      "head_score": 0.0
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "components": [
    {
      "value": 0,
      "factor": "head",
      "weight": 0.1,
      "points": 0.0,
      "present": true,
      "area": 0
    },
    {
      "value": 0,
      "factor": "upper_extremities",
      "weight": 0.2,
      "points": 0.0,
      "present": true,
      "area": 0
    },
    {
      "value": 0,
      "factor": "trunk",
      "weight": 0.3,
      "points": 0.0,
      "present": true,
      "area": 0
    },
    {
      "value": 0,
      "factor": "lower_extremities",
      "weight": 0.4,
      "points": 0.0,
      "present": true,
      "area": 0
    }
  ],
  "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Fredriksson T, Pettersson U",
    "doi": "10.1159/000250839",
    "id": "fredriksson-1978",
    "pmid": "357213",
    "source": "Dermatologica. 1978;157(4):238-244",
    "title": "Severe psoriasis--oral therapy with a new retinoid"
  },
  "formula": "pasi",
  "formula_expression": "PASI = 0.1*(head_erythema + head_induration + head_scaling)*head_area + 0.2*(upper_extremities_erythema + upper_extremities_induration + upper_extremities_scaling)*upper_extremities_area + 0.3*(trunk_erythema + trunk_induration + trunk_scaling)*trunk_area + 0.4*(lower_extremities_erythema + lower_extremities_induration + lower_extremities_scaling)*lower_extremities_area; each area integer 0-6 (0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%); each of erythema, induration, and scaling integer 0-4 (0 none, 1 slight, 2 moderate, 3 severe, 4 very severe); adult region weights head 0.1, upper extremities 0.2, trunk 0.3, lower extremities 0.4; max 72; magent uses these adult weights only; this paper published no Investigator Global Assessment or mild-moderate-severe PASI cutoffs",
  "max_score": 72,
  "score": 0.0,
  "lower_extremities_score": 0.0,
  "trunk_score": 0.0,
  "upper_extremities_score": 0.0,
  "head_score": 0.0
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• EASI — Compute Hanifin 2001 EASI from four body regions. For each region the caller assigns area 0-6 and four intensity signs (erythema, edema/papulation, excoriation, lichenification) each 0-3. Region score = (sum of 4 signs) × area × adult weight. Total EASI is the sum (max 72).
• UAS — Sum Młynek 2008 EAACI/GA2LEN/EDF urticaria activity score over seven consecutive days: each day wheals 0-3 plus pruritus 0-3 (daily UAS 0-6). Return UAS7 (0-42) and mean_daily_uas. This paper published no UAS7 activity bands.

Payment

Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /docs/mcp.

Guarantees

• HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON.
• exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE.
• HTTP 402 is unpaid only. Do not sign a second authorization because of a 503.
• Execution is timeout-bounded and concurrency-capped.
• Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.