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Crohn's disease activity index (CDAI)

CDAI

Compute the Best 1976 Crohn's disease activity index from eight caller-assigned variables and return the rounded integer score. Does not return later trial activity bands.

LIVE $0.005 USDC GET /api/calc/cdai

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

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

What it computes

Compute the Best 1976 Crohn's disease activity index from eight caller-assigned variables and return the rounded integer score. Does not return later trial activity bands.

When to use

When an agent already has Best 1976 seven-day stool, pain, and well-being sums, extra-intestinal count, antidiarrheal flag, abdominal mass (0/2/5), hematocrit, sex, and caller-assigned weight-percent deviation and needs the weighted index, not a Crohn's diagnosis, Harvey-Bradshaw one-day index, or later trial cutoffs.

When not to use

• Not a medical device and not a Crohn's diagnosis or a treatment order.
• magent does not examine the patient. Seven-day sums, extra-intestinal count, antidiarrheal use, abdominal mass, hematocrit, and weight-percent deviation are caller-assigned.
• Abdominal mass is Best 1976 0 (none), 2 (questionable), or 5 (definite), not 1/3/4. Extra-intestinal count is 0-6; magent does not enumerate the six findings as separate params.
• magent returns the integer index only and does not apply later trial activity bands. Liquid-stool 0-70, hematocrit 10-70, and weight-percent -50 to 80 are magent clamps, not published maxima.

Formula

CDAI = liquid_stool_count_7d*2 + abdominal_pain_sum_7d*5 + wellbeing_sum_7d*7 + extra_intestinal_count*20 + taking_antidiarrheal*30 + abdominal_mass*10 + hematocrit_deficit*6 + weight_percent_deviation; hematocrit_deficit = 47-hematocrit_percent (male) or 42-hematocrit_percent (female); Best 1976; score rounded after the weight term

Citation

Title

Development of a Crohn's disease activity index. National Cooperative Crohn's Disease Study

Authors

Best WR, Becktel JM, Singleton JW, Kern F Jr

Source

Gastroenterology. 1976;70(3):439-444

DOI

10.1016/S0016-5085(76)80163-1

Worked example

Also searched as

• Crohn's Disease Activity Index
• CDAI
• Best CDAI
• National Cooperative Crohn's Disease Study
• Crohn's activity index
• Best 1976 CDAI

Try

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

/api/calc/cdai?sex=male&liquid_stool_count_7d=0&abdominal_pain_sum_7d=0&wellbeing_sum_7d=0&extra_intestinal_count=0&taking_antidiarrheal=false&abdominal_mass=0&hematocrit_percent=47&weight_percent_deviation=0

Full URL: https://api.magentlab.com/api/calc/cdai?sex=male&liquid_stool_count_7d=0&abdominal_pain_sum_7d=0&wellbeing_sum_7d=0&extra_intestinal_count=0&taking_antidiarrheal=false&abdominal_mass=0&hematocrit_percent=47&weight_percent_deviation=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/cdai?sex=male&liquid_stool_count_7d=0&abdominal_pain_sum_7d=0&wellbeing_sum_7d=0&extra_intestinal_count=0&taking_antidiarrheal=false&abdominal_mass=0&hematocrit_percent=47&weight_percent_deviation=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/cdai 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": [
    {
      "abdominal_mass": "0",
      "abdominal_pain_sum_7d": "0",
      "extra_intestinal_count": "0",
      "hematocrit_percent": "47",
      "liquid_stool_count_7d": "0",
      "sex": "male",
      "taking_antidiarrheal": "false",
      "weight_percent_deviation": "0",
      "wellbeing_sum_7d": "0"
    },
    {
      "abdominal_mass": "0",
      "abdominal_pain_sum_7d": "0",
      "extra_intestinal_count": "0",
      "hematocrit_percent": "47",
      "liquid_stool_count_7d": "0",
      "sex": "male",
      "taking_antidiarrheal": "false",
      "weight_percent_deviation": "0",
      "wellbeing_sum_7d": "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/cdai",
  "items": [
    {
      "components": [
        {
          "value": 0,
          "factor": "liquid_stool_count_7d",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "abdominal_pain_sum_7d",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "wellbeing_sum_7d",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "extra_intestinal_count",
          "points": 0,
          "present": true
        },
        {
          "factor": "taking_antidiarrheal",
          "points": 0,
          "present": false
        },
        {
          "value": 0,
          "factor": "abdominal_mass",
          "points": 0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "hematocrit_deficit",
          "points": 0.0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "weight_percent_deviation",
          "points": 0.0,
          "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": "Best WR, Becktel JM, Singleton JW, Kern F Jr",
        "doi": "10.1016/S0016-5085(76)80163-1",
        "id": "best-1976",
        "pmid": "1248701",
        "source": "Gastroenterology. 1976;70(3):439-444",
        "title": "Development of a Crohn's disease activity index. National Cooperative Crohn's Disease Study"
      },
      "formula": "cdai",
      "formula_expression": "CDAI = liquid_stool_count_7d*2 + abdominal_pain_sum_7d*5 + wellbeing_sum_7d*7 + extra_intestinal_count*20 + taking_antidiarrheal*30 + abdominal_mass*10 + hematocrit_deficit*6 + weight_percent_deviation; hematocrit_deficit = 47-hematocrit_percent (male) or 42-hematocrit_percent (female); Best 1976; score rounded after the weight term",
      "score": 0,
      "hematocrit_percent": 47.0,
      "sex": "male",
      "abdominal_mass": 0,
      "abdominal_pain_sum_7d": 0,
      "extra_intestinal_count": 0,
      "hematocrit_deficit": 0.0,
      "liquid_stool_count_7d": 0,
      "taking_antidiarrheal": false,
      "weight_percent_deviation": 0.0,
      "wellbeing_sum_7d": 0
    },
    {
      "components": [
        {
          "value": 0,
          "factor": "liquid_stool_count_7d",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "abdominal_pain_sum_7d",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "wellbeing_sum_7d",
          "points": 0,
          "present": true
        },
        {
          "value": 0,
          "factor": "extra_intestinal_count",
          "points": 0,
          "present": true
        },
        {
          "factor": "taking_antidiarrheal",
          "points": 0,
          "present": false
        },
        {
          "value": 0,
          "factor": "abdominal_mass",
          "points": 0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "hematocrit_deficit",
          "points": 0.0,
          "present": true
        },
        {
          "value": 0.0,
          "factor": "weight_percent_deviation",
          "points": 0.0,
          "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": "Best WR, Becktel JM, Singleton JW, Kern F Jr",
        "doi": "10.1016/S0016-5085(76)80163-1",
        "id": "best-1976",
        "pmid": "1248701",
        "source": "Gastroenterology. 1976;70(3):439-444",
        "title": "Development of a Crohn's disease activity index. National Cooperative Crohn's Disease Study"
      },
      "formula": "cdai",
      "formula_expression": "CDAI = liquid_stool_count_7d*2 + abdominal_pain_sum_7d*5 + wellbeing_sum_7d*7 + extra_intestinal_count*20 + taking_antidiarrheal*30 + abdominal_mass*10 + hematocrit_deficit*6 + weight_percent_deviation; hematocrit_deficit = 47-hematocrit_percent (male) or 42-hematocrit_percent (female); Best 1976; score rounded after the weight term",
      "score": 0,
      "hematocrit_percent": 47.0,
      "sex": "male",
      "abdominal_mass": 0,
      "abdominal_pain_sum_7d": 0,
      "extra_intestinal_count": 0,
      "hematocrit_deficit": 0.0,
      "liquid_stool_count_7d": 0,
      "taking_antidiarrheal": false,
      "weight_percent_deviation": 0.0,
      "wellbeing_sum_7d": 0
    }
  ]
}

Response

Example JSON

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

{
  "components": [
    {
      "value": 0,
      "factor": "liquid_stool_count_7d",
      "points": 0,
      "present": true
    },
    {
      "value": 0,
      "factor": "abdominal_pain_sum_7d",
      "points": 0,
      "present": true
    },
    {
      "value": 0,
      "factor": "wellbeing_sum_7d",
      "points": 0,
      "present": true
    },
    {
      "value": 0,
      "factor": "extra_intestinal_count",
      "points": 0,
      "present": true
    },
    {
      "factor": "taking_antidiarrheal",
      "points": 0,
      "present": false
    },
    {
      "value": 0,
      "factor": "abdominal_mass",
      "points": 0,
      "present": true
    },
    {
      "value": 0.0,
      "factor": "hematocrit_deficit",
      "points": 0.0,
      "present": true
    },
    {
      "value": 0.0,
      "factor": "weight_percent_deviation",
      "points": 0.0,
      "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": "Best WR, Becktel JM, Singleton JW, Kern F Jr",
    "doi": "10.1016/S0016-5085(76)80163-1",
    "id": "best-1976",
    "pmid": "1248701",
    "source": "Gastroenterology. 1976;70(3):439-444",
    "title": "Development of a Crohn's disease activity index. National Cooperative Crohn's Disease Study"
  },
  "formula": "cdai",
  "formula_expression": "CDAI = liquid_stool_count_7d*2 + abdominal_pain_sum_7d*5 + wellbeing_sum_7d*7 + extra_intestinal_count*20 + taking_antidiarrheal*30 + abdominal_mass*10 + hematocrit_deficit*6 + weight_percent_deviation; hematocrit_deficit = 47-hematocrit_percent (male) or 42-hematocrit_percent (female); Best 1976; score rounded after the weight term",
  "score": 0,
  "hematocrit_percent": 47.0,
  "sex": "male",
  "abdominal_mass": 0,
  "abdominal_pain_sum_7d": 0,
  "extra_intestinal_count": 0,
  "hematocrit_deficit": 0.0,
  "liquid_stool_count_7d": 0,
  "taking_antidiarrheal": false,
  "weight_percent_deviation": 0.0,
  "wellbeing_sum_7d": 0
}

Client errors (HTTP 400)

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

Related tools

• HBI — Sum Harvey 1980 simple-index items (previous-day well-being, abdominal pain, liquid stools, abdominal mass, and one point per listed complication) and return the total. Does not return later remission or activity bands.
• Mayo DAI — Sum four caller-assigned Schroeder 1987 ulcerative colitis disease-activity index items (each integer 0-3) and return the total (max 12). Does not return later remission or activity bands.
• PUCAI — Sum six caller-assigned Turner 2007 PUCAI item points and return the published total (max 85) with activity band.

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.