Simplified Disease Activity Index (SDAI)

SDAI

Sum caller-assigned 28-joint swollen and tender counts, 0–10 cm patient and evaluator globals, and CRP in mg/dL, and return the Aletaha 2005 SDAI with the newly proposed activity state.

LIVE $0.005 USDC GET /api/calc/sdai

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

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

What it computes

Sum caller-assigned 28-joint swollen and tender counts, 0–10 cm patient and evaluator globals, and CRP in mg/dL, and return the Aletaha 2005 SDAI with the newly proposed activity state.

When to use

When an agent already has 28-joint swollen and tender counts, 0–10 cm patient and evaluator globals, and CRP in mg/dL and needs the published SDAI sum and Aletaha 2005 newly proposed activity state, not the original 5/20/40 cutoffs.

When not to use

Not a medical device and not a rheumatoid arthritis diagnosis or a treatment order.
magent does not count joints or assay CRP. sjc28, tjc28, pga, ega, and crp_mg_dl are caller-assigned. CRP is mg/dL as published, not mg/L. The 0–30 CRP range is a magent clamp.
Uses the Aletaha 2005 newly proposed SDAI definition (≤3.3 remission, ≤11 low, ≤26 moderate, >26 high), not the original 5/20/40 cutoffs.
Not CDAI (SDAI without CRP). Not Crohn's CDAI. Not DAS28.

Formula

SDAI = sjc28 + tjc28 + pga + ega + crp_mg_dl; Aletaha 2005 newly proposed definition; ≤3.3 remission, >3.3 and ≤11 low, >11 and ≤26 moderate, >26 high; half points allowed; not original 5/20/40; magent does not count joints or assay CRP

Citation

Title: Remission and active disease in rheumatoid arthritis: defining criteria for disease activity states
Authors: Aletaha D, Ward MM, Machold KP, Nell VPK, Stamm T, Smolen JS
Source: Arthritis Rheum. 2005;52(9):2625-2636
DOI: 10.1002/art.21235

Worked example

CRP 0.4 mg/dL, clinical zeros

Given: crp_mg_dl=0.4ega=0pga=0sjc28=0tjc28=0

sjc28 0 + tjc28 0 + pga 0 + ega 0 + crp_mg_dl 0.4
score = 0.4 (≤3.3), sdai_band remission

Score 3.3 is remission

Given: crp_mg_dl=0ega=0pga=3.3sjc28=0tjc28=0

pga 3.3; remaining terms 0
score = 3.3 (≤3.3), sdai_band remission

Also searched as

Simplified Disease Activity Index
SDAI
Aletaha SDAI
rheumatoid arthritis SDAI
SDAI disease activity
RA simplified disease activity

Try

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

/api/calc/sdai?sjc28=0&tjc28=0&pga=0&ega=0&crp_mg_dl=0.4

Full URL: https://api.magentlab.com/api/calc/sdai?sjc28=0&tjc28=0&pga=0&ega=0&crp_mg_dl=0.4

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/sdai?sjc28=0&tjc28=0&pga=0&ega=0&crp_mg_dl=0.4"

Parameters

Name	Type	Required	Description
`sjc28`	integer	required	Caller-assigned swollen joint count on the 28-joint set (Aletaha 2005). Integer 0-28. magent does not count joints.
`tjc28`	integer	required	Caller-assigned tender joint count on the 28-joint set (Aletaha 2005). Integer 0-28. magent does not count joints.
`pga`	number	required	Caller-assigned patient global assessment on a 0-10 cm VAS (Aletaha 2005). Number 0-10. magent does not examine the patient.
`ega`	number	required	Caller-assigned evaluator global assessment on a 0-10 cm VAS (Aletaha 2005). Number 0-10. magent does not examine the patient.
`crp_mg_dl`	number	required	Caller-assigned C-reactive protein in mg/dL (Aletaha 2005; not mg/L). Number 0-30 is a magent clamp. magent does not assay CRP.

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/sdai 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": [
    {
      "crp_mg_dl": "0.4",
      "ega": "0",
      "pga": "0",
      "sjc28": "0",
      "tjc28": "0"
    },
    {
      "crp_mg_dl": "0.4",
      "ega": "0",
      "pga": "0",
      "sjc28": "0",
      "tjc28": "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/sdai",
  "items": [
    {
      "components": [
        {
          "value": 0,
          "factor": "sjc28",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "tjc28",
          "points": 0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "pga",
          "points": 0.0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "ega",
          "points": 0.0,
          "present": true
        },
        {
          "value": 0.4,
          "factor": "crp_mg_dl",
          "points": 0.4,
          "present": true
        }
      ],
      "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": "Aletaha D, Ward MM, Machold KP, Nell VPK, Stamm T, Smolen JS",
        "doi": "10.1002/art.21235",
        "id": "aletaha-2005",
        "pmid": "16142705",
        "source": "Arthritis Rheum. 2005;52(9):2625-2636",
        "title": "Remission and active disease in rheumatoid arthritis: defining criteria for disease activity states"
      },
      "formula": "sdai",
      "formula_expression": "SDAI = sjc28 + tjc28 + pga + ega + crp_mg_dl; Aletaha 2005 newly proposed definition; ≤3.3 remission, >3.3 and ≤11 low, >11 and ≤26 moderate, >26 high; half points allowed; not original 5/20/40; magent does not count joints or assay CRP",
      "max_score": 106,
      "score": 0.4,
      "crp_mg_dl": 0.4,
      "ega": 0.0,
      "pga": 0.0,
      "sdai_band": "remission",
      "sjc28": 0,
      "tjc28": 0
    },
    {
      "components": [
        {
          "value": 0,
          "factor": "sjc28",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "tjc28",
          "points": 0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "pga",
          "points": 0.0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "ega",
          "points": 0.0,
          "present": true
        },
        {
          "value": 0.4,
          "factor": "crp_mg_dl",
          "points": 0.4,
          "present": true
        }
      ],
      "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": "Aletaha D, Ward MM, Machold KP, Nell VPK, Stamm T, Smolen JS",
        "doi": "10.1002/art.21235",
        "id": "aletaha-2005",
        "pmid": "16142705",
        "source": "Arthritis Rheum. 2005;52(9):2625-2636",
        "title": "Remission and active disease in rheumatoid arthritis: defining criteria for disease activity states"
      },
      "formula": "sdai",
      "formula_expression": "SDAI = sjc28 + tjc28 + pga + ega + crp_mg_dl; Aletaha 2005 newly proposed definition; ≤3.3 remission, >3.3 and ≤11 low, >11 and ≤26 moderate, >26 high; half points allowed; not original 5/20/40; magent does not count joints or assay CRP",
      "max_score": 106,
      "score": 0.4,
      "crp_mg_dl": 0.4,
      "ega": 0.0,
      "pga": 0.0,
      "sdai_band": "remission",
      "sjc28": 0,
      "tjc28": 0
    }
  ]
}

Response

Field	Type	Description
`formula`	string	sdai
`formula_expression`	string	Exact expression used
`score`	number	SDAI sum sjc28 + tjc28 + pga + ega + crp_mg_dl. Not integer-rounded; half points allowed. Theoretical max 106.
`max_score`	integer	Always 106 (28+28+10+10+30 magent CRP clamp)
`sdai_band`	string	Aletaha 2005 newly proposed SDAI state: remission (≤3.3), low (>3.3 and ≤11), moderate (>11 and ≤26), or high (>26). Not original 5/20/40.
`sjc28`	integer	Swollen 28-joint count used
`tjc28`	integer	Tender 28-joint count used
`pga`	number	Patient global 0-10 cm VAS used
`ega`	number	Evaluator global 0-10 cm VAS used
`crp_mg_dl`	number	CRP in mg/dL used
`components`	array	Per-variable points
`citation`	object	Aletaha et al. Arthritis Rheum 2005 citation
`disclaimer`	string	Not-a-device notice

Example JSON

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

{
  "components": [
    {
      "value": 0,
      "factor": "sjc28",
      "points": 0,
      "present": true
    },
    {
      "value": 0,
      "factor": "tjc28",
      "points": 0,
      "present": true
    },
    {
      "value": 0.0,
      "factor": "pga",
      "points": 0.0,
      "present": true
    },
    {
      "value": 0.0,
      "factor": "ega",
      "points": 0.0,
      "present": true
    },
    {
      "value": 0.4,
      "factor": "crp_mg_dl",
      "points": 0.4,
      "present": true
    }
  ],
  "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": "Aletaha D, Ward MM, Machold KP, Nell VPK, Stamm T, Smolen JS",
    "doi": "10.1002/art.21235",
    "id": "aletaha-2005",
    "pmid": "16142705",
    "source": "Arthritis Rheum. 2005;52(9):2625-2636",
    "title": "Remission and active disease in rheumatoid arthritis: defining criteria for disease activity states"
  },
  "formula": "sdai",
  "formula_expression": "SDAI = sjc28 + tjc28 + pga + ega + crp_mg_dl; Aletaha 2005 newly proposed definition; ≤3.3 remission, >3.3 and ≤11 low, >11 and ≤26 moderate, >26 high; half points allowed; not original 5/20/40; magent does not count joints or assay CRP",
  "max_score": 106,
  "score": 0.4,
  "crp_mg_dl": 0.4,
  "ega": 0.0,
  "pga": 0.0,
  "sdai_band": "remission",
  "sjc28": 0,
  "tjc28": 0
}

Client errors (HTTP 400)

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

HTTP	Code	When
400	`invalid_sdai`	sjc28 and tjc28 must be integers 0–28; pga and ega numbers 0–10; crp_mg_dl a number 0–30 (Aletaha 2005 SDAI disease-activity states). Returned before settlement; you are not charged.
400	`invalid_items`	POST body must be a JSON object with only an items array Returned before settlement; you are not charged.
400	`invalid_item_count`	items must be an array of 1 to 25 objects Returned before settlement; you are not charged.
400	`invalid_item`	each items entry must be a JSON object Returned before settlement; you are not charged.

Related tools

ACR/EULAR gout — Apply the 2015 ACR/EULAR gout classification criteria (Neogi Table 2): require the entry episode, classify immediately if MSU crystals are present, otherwise return the Step 3 score (max 23) and whether score ≥8 classifies gout. Not a gout diagnosis.
ACR/EULAR PMR — Apply the 2012 EULAR/ACR polymyalgia rheumatica classification criteria (Dasgupta Table 4): require age ≥50, bilateral shoulder aching, and abnormal CRP and/or ESR, then return the clinical score with or without optional ultrasound and whether the published cut point classifies PMR. Not a PMR diagnosis.
ACR/EULAR Sjögren — Apply the 2016 ACR/EULAR classification criteria for primary Sjögren's syndrome (Shiboski Table 3): require published inclusion and no exclusion, then return the five-item weighted score and whether the ≥4 cut point classifies primary Sjögren's syndrome. Not a diagnosis.

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.