# Psoriasis Area and Severity Index (PASI) PASI Status: LIVE Price: $0.005 USDC `GET /api/calc/pasi` HTML: https://magentlab.com/docs/pasi Markdown: https://magentlab.com/docs/pasi.md 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 [Severe psoriasis--oral therapy with a new retinoid](https://doi.org/10.1159/000250839) Fredriksson T, Pettersson U Dermatologica. 1978;157(4):238-244 DOI: [10.1159/000250839](https://doi.org/10.1159/000250839) ## Worked example ### All zeros Given: `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` 1. every region area 0 and every sign 0 as assigned by the caller 2. each region score = 0; PASI = 0 (max 72). This paper published no IGA or mild-moderate-severe PASI cutoff. ### All regions at published maximum Given: `head_area=6, head_erythema=4, head_induration=4, head_scaling=4, lower_extremities_area=6, lower_extremities_erythema=4, lower_extremities_induration=4, lower_extremities_scaling=4, trunk_area=6, trunk_erythema=4, trunk_induration=4, trunk_scaling=4, upper_extremities_area=6, upper_extremities_erythema=4, upper_extremities_induration=4, upper_extremities_scaling=4` 1. each area 6 and each of erythema, induration, and scaling 4 as assigned by the caller 2. head 12×6×0.1 = 7.2; upper extremities 12×6×0.2 = 14.4; trunk 12×6×0.3 = 21.6; lower extremities 12×6×0.4 = 28.8; PASI = 72 (max 72). No IGA or severity band. ## Also searched as - PASI - Psoriasis Area and Severity Index - Fredriksson PASI - PASI score - psoriasis severity index - Fredriksson 1978 PASI - psoriasis area severity - PASI 72 ## Parameters - `head_area` (integer, required): Caller-assigned Fredriksson 1978 PASI area of involvement for this body region (integer 0-6): 0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%. magent does not examine the skin. - `head_erythema` (integer, required): Caller-assigned Fredriksson 1978 PASI erythema for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `head_induration` (integer, required): Caller-assigned Fredriksson 1978 PASI induration for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `head_scaling` (integer, required): Caller-assigned Fredriksson 1978 PASI scaling for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `upper_extremities_area` (integer, required): Caller-assigned Fredriksson 1978 PASI area of involvement for this body region (integer 0-6): 0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%. magent does not examine the skin. - `upper_extremities_erythema` (integer, required): Caller-assigned Fredriksson 1978 PASI erythema for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `upper_extremities_induration` (integer, required): Caller-assigned Fredriksson 1978 PASI induration for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `upper_extremities_scaling` (integer, required): Caller-assigned Fredriksson 1978 PASI scaling for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `trunk_area` (integer, required): Caller-assigned Fredriksson 1978 PASI area of involvement for this body region (integer 0-6): 0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%. magent does not examine the skin. - `trunk_erythema` (integer, required): Caller-assigned Fredriksson 1978 PASI erythema for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `trunk_induration` (integer, required): Caller-assigned Fredriksson 1978 PASI induration for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `trunk_scaling` (integer, required): Caller-assigned Fredriksson 1978 PASI scaling for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `lower_extremities_area` (integer, required): Caller-assigned Fredriksson 1978 PASI area of involvement for this body region (integer 0-6): 0 none, 1 <10%, 2 10-29%, 3 30-49%, 4 50-69%, 5 70-89%, 6 90-100%. magent does not examine the skin. - `lower_extremities_erythema` (integer, required): Caller-assigned Fredriksson 1978 PASI erythema for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `lower_extremities_induration` (integer, required): Caller-assigned Fredriksson 1978 PASI induration for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. - `lower_extremities_scaling` (integer, required): Caller-assigned Fredriksson 1978 PASI scaling for this region (integer 0-4): 0 none, 1 slight, 2 moderate, 3 severe, 4 very severe. magent does not examine the skin. ## 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. Method: `POST /api/calc/pasi` Max items: 25 Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic) Status: 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: ```json { "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" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/pasi Example 200: ```json { "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 fields - `formula` (string): pasi - `formula_expression` (string): Exact expression used - `score` (number): Fredriksson 1978 PASI total from four adult-weighted regions (0-72) - `max_score` (integer): Always 72 - `head_score` (number): Head region: (erythema + induration + scaling) × area × 0.1 - `upper_extremities_score` (number): Upper extremities region: (erythema + induration + scaling) × area × 0.2 - `trunk_score` (number): Trunk region: (erythema + induration + scaling) × area × 0.3 - `lower_extremities_score` (number): Lower extremities region: (erythema + induration + scaling) × area × 0.4 - `components` (array): Per-region caller-assigned PASI contribution - `citation` (object): Fredriksson and Pettersson Dermatologica 1978 citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "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 } ``` ## Errors - HTTP 400 `invalid_pasi`: each PASI region needs area 0-6 and erythema, induration, and scaling 0-4 (Fredriksson 1978). Returned before settlement; you are not charged. - HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged. - HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged. - HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged. Shared HTTP 402 and 503: https://magentlab.com/docs/payments ## Related tools - [EASI](https://magentlab.com/docs/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](https://magentlab.com/docs/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. - GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall). - HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote. - Sign accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering. - Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional. - Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact nonce only after a new HTTP 402. - offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront. - offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization. - not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search. Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers). Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments Stdio MCP (one process per host): https://magentlab.com/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.