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Light's criteria (pleural fluid)

Light's criteria

Apply Light 1972 pleural fluid criteria from protein ratio, LDH ratio, and pleural LDH versus two-thirds the laboratory LDH upper limit of normal.

Also searched as

• Light's criteria
• Light criteria pleural
• transudate vs exudate
• pleural fluid LDH
• pleural protein ratio
• Light 1972 effusion

LIVE $0.005 USDC GET /api/calc/lights

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

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

What it computes

Apply Light 1972 pleural fluid criteria from protein ratio, LDH ratio, and pleural LDH versus two-thirds the laboratory LDH upper limit of normal.

When to use

When an agent needs Light 1972 transudate versus exudate arithmetic and must not invent Heffner abbreviated criteria, an NT-proBNP rule, or a cause of the effusion.

When not to use

• Not a diagnosis of the cause of an effusion (for example CHF versus infection).
• Not Heffner's abbreviated two-test criteria and not an NT-proBNP rule.
• magent does not interpret a chest x-ray.
• ldh_uln_u_l is required; magent does not assume a laboratory ULN of 200 U/L.
• Cutoffs are strictly greater than 0.5, 0.6, and two-thirds ULN (equality is not exudate by that criterion).

Formula

exudate if pleural_protein_g_dl / serum_protein_g_dl > 0.5 or pleural_ldh_u_l / serum_ldh_u_l > 0.6 or pleural_ldh_u_l > (2/3) * ldh_uln_u_l

Citation

Title

Pleural effusions: the diagnostic separation of transudates and exudates

Authors

Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr

Source

Ann Intern Med. 1972;77(4):507-513

DOI

10.7326/0003-4819-77-4-507

Worked example

Try

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

/api/calc/lights?pleural_protein_g_dl=3.0&serum_protein_g_dl=6.0&pleural_ldh_u_l=100&serum_ldh_u_l=200&ldh_uln_u_l=200

Full URL: https://api.magentlab.com/api/calc/lights?pleural_protein_g_dl=3.0&serum_protein_g_dl=6.0&pleural_ldh_u_l=100&serum_ldh_u_l=200&ldh_uln_u_l=200

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/lights?pleural_protein_g_dl=3.0&serum_protein_g_dl=6.0&pleural_ldh_u_l=100&serum_ldh_u_l=200&ldh_uln_u_l=200"

Parameters

Bulk (POST)

POST the same path with a JSON items array. Price is n times the GET unit. Invalid items return HTTP 400 before settlement.

POST /api/calc/lights Max 25 unit_amount * n PREVIEW

• 1 to 25 items. Each item uses the same keys as the GET query parameters.
• 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": [
    {
      "ldh_uln_u_l": "200",
      "pleural_ldh_u_l": "100",
      "pleural_protein_g_dl": "3.0",
      "serum_ldh_u_l": "200",
      "serum_protein_g_dl": "6.0"
    },
    {
      "ldh_uln_u_l": "200",
      "pleural_ldh_u_l": "100",
      "pleural_protein_g_dl": "3.0",
      "serum_ldh_u_l": "200",
      "serum_protein_g_dl": "6.0"
    }
  ]
}

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/lights",
  "items": [
    {
      "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": "Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr",
        "doi": "10.7326/0003-4819-77-4-507",
        "id": "light-1972",
        "source": "Ann Intern Med. 1972;77(4):507-513",
        "title": "Pleural effusions: the diagnostic separation of transudates and exudates"
      },
      "formula": "lights",
      "formula_expression": "exudate if pleural_protein_g_dl / serum_protein_g_dl > 0.5 or pleural_ldh_u_l / serum_ldh_u_l > 0.6 or pleural_ldh_u_l > (2/3) * ldh_uln_u_l",
      "criteria": [
        {
          "value": 0.5,
          "factor": "protein_ratio_gt_0_5",
          "met": false
        },
        {
          "value": 0.5,
          "factor": "ldh_ratio_gt_0_6",
          "met": false
        },
        {
          "value": 100.0,
          "factor": "pleural_ldh_gt_two_thirds_uln",
          "met": false
        }
      ],
      "exudate": false,
      "ldh_ratio": 0.5,
      "ldh_two_thirds_uln": 133.3,
      "pleural_ldh_u_l": 100.0,
      "protein_ratio": 0.5
    },
    {
      "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": "Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr",
        "doi": "10.7326/0003-4819-77-4-507",
        "id": "light-1972",
        "source": "Ann Intern Med. 1972;77(4):507-513",
        "title": "Pleural effusions: the diagnostic separation of transudates and exudates"
      },
      "formula": "lights",
      "formula_expression": "exudate if pleural_protein_g_dl / serum_protein_g_dl > 0.5 or pleural_ldh_u_l / serum_ldh_u_l > 0.6 or pleural_ldh_u_l > (2/3) * ldh_uln_u_l",
      "criteria": [
        {
          "value": 0.5,
          "factor": "protein_ratio_gt_0_5",
          "met": false
        },
        {
          "value": 0.5,
          "factor": "ldh_ratio_gt_0_6",
          "met": false
        },
        {
          "value": 100.0,
          "factor": "pleural_ldh_gt_two_thirds_uln",
          "met": false
        }
      ],
      "exudate": false,
      "ldh_ratio": 0.5,
      "ldh_two_thirds_uln": 133.3,
      "pleural_ldh_u_l": 100.0,
      "protein_ratio": 0.5
    }
  ]
}

Response

Example JSON

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

{
  "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": "Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr",
    "doi": "10.7326/0003-4819-77-4-507",
    "id": "light-1972",
    "source": "Ann Intern Med. 1972;77(4):507-513",
    "title": "Pleural effusions: the diagnostic separation of transudates and exudates"
  },
  "formula": "lights",
  "formula_expression": "exudate if pleural_protein_g_dl / serum_protein_g_dl > 0.5 or pleural_ldh_u_l / serum_ldh_u_l > 0.6 or pleural_ldh_u_l > (2/3) * ldh_uln_u_l",
  "criteria": [
    {
      "value": 0.5,
      "factor": "protein_ratio_gt_0_5",
      "met": false
    },
    {
      "value": 0.5,
      "factor": "ldh_ratio_gt_0_6",
      "met": false
    },
    {
      "value": 100.0,
      "factor": "pleural_ldh_gt_two_thirds_uln",
      "met": false
    }
  ],
  "exudate": false,
  "ldh_ratio": 0.5,
  "ldh_two_thirds_uln": 133.3,
  "pleural_ldh_u_l": 100.0,
  "protein_ratio": 0.5
}

Client errors (HTTP 400)

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

Related tools

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Payment

Required query parameters must be present and valid. 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

• Invalid query parameters return HTTP 400 before settlement. You are not charged.
• Settlement finishes before the tool executes (paymentFlow upfront). 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.