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Light's Criteria Pleural Fluid Calculator
x402
Light's Criteria Pleural Fluid Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).
Applies Light's 1972 criteria to classify pleural fluid as exudate or transudate using protein and LDH ratios against a caller-supplied LDH upper limit of normal
Price / call$0.005
Success—
StatusUnknown
How this service works
Light 1972 pleural fluid criteria: exudate if protein ratio > 0.5, LDH ratio > 0.6, or pleural LDH > two-thirds the laboratory LDH ULN. ULN is required; magent does not assume 200 U/L. Strictly greater than those cutoffs. Deterministic published arithmetic with citation; not a diagnosis of cause, not Heffner's abbreviated criteria, and not a chest x-ray interpretation.
Output
Returns a deterministic classification of the pleural fluid as exudate or transudate based on Light's three criteria: (1) pleural-to-serum protein ratio > 0.5, (2) pleural-to-serum LDH ratio > 0.6, (3) pleural LDH > two-thirds the caller-supplied LDH ULN. Output includes individual ratio values, which criteria are met, and the overall classification. Not a diagnosis of cause and not Heffner's abbreviated criteria.
Example use cases
Thoracentesis result interpretation
“I just got back pleural fluid results — pleural protein is 3.9 g/dL, serum protein 7.1 g/dL, pleural LDH 180 U/L, serum LDH 190 U/L, and our lab's LDH ULN is 220 U/L. Run Light's criteria and tell me if it's an exudate or transudate.”
Automated EMR lab result triage
“For this patient's pleural fluid panel — pleural protein 1.8 g/dL, serum protein 6.5 g/dL, pleural LDH 45 U/L, serum LDH 155 U/L, lab LDH ULN is 200 U/L — apply Light's 1972 criteria and flag which of the three criteria, if any, are met.”
Medical education case review
“Walk me through Light's criteria calculation for a teaching case: pleural protein 5.1 g/dL, serum protein 6.9 g/dL, pleural LDH 410 U/L, serum LDH 250 U/L, and the lab's LDH upper limit of normal is 230 U/L — show each ratio and the final exudate or transudate conclusion.”
Technical details
Endpoint
GEThttps://api.magentlab.com/api/calc/lightsWhen to prefer
Use this endpoint when you need a strictly correct, citeable implementation of Light's 1972 original three-criterion rule — specifically when you must supply the laboratory's own LDH ULN rather than assuming 200 U/L. Prefer this over manual calculation to avoid arithmetic errors and to get structured, auditable output for clinical documentation or decision support pipelines. Do not use if you need Heffner's abbreviated criteria or a diagnosis of pleural disease cause.
Side effects
- Missing required parameters (pleural_protein_g_dl, serum_protein_g_dl, pleural_ldh_u_l, serum_ldh_u_l, ldh_uln_u_l) returns validation error
- Values outside allowed ranges (e.g. LDH ULN outside 50–2000 U/L) return 400-level error
- Payment failure or insufficient USDC balance returns 402 Payment Required
- Passing 0 for any parameter may cause division-by-zero or range rejection
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"path": "/api/calc/lights",
"count": 2,
"items": [
{
"exudate": false,
"formula": "lights",
"citation": {
"id": "light-1972",
"doi": "10.7326/0003-4819-77-4-507",
"title": "Pleural effusions: the diagnostic separation of transudates and exudates",
"source": "Ann Intern Med. 1972;77(4):507-513",
"authors": "Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr"
},
"criteria": [
{
"met": false,
"value": 0.5,
"factor": "protein_ratio_gt_0_5"
},
{
"met": false,
"value": 0.5,
"factor": "ldh_ratio_gt_0_6"
},
{
"met": false,
"value": 100,
"factor": "pleural_ldh_gt_two_thirds_uln"
}
],
"ldh_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.",
"protein_ratio": 0.5,
"pleural_ldh_u_l": 100,
"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",
"ldh_two_thirds_uln": 133.3
},
{
"exudate": false,
"formula": "lights",
"citation": {
"id": "light-1972",
"doi": "10.7326/0003-4819-77-4-507",
"title": "Pleural effusions: the diagnostic separation of transudates and exudates",
"source": "Ann Intern Med. 1972;77(4):507-513",
"authors": "Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr"
},
"criteria": [
{
"met": false,
"value": 0.5,
"factor": "protein_ratio_gt_0_5"
},
{
"met": false,
"value": 0.5,
"factor": "ldh_ratio_gt_0_6"
},
{
"met": false,
"value": 100,
"factor": "pleural_ldh_gt_two_thirds_uln"
}
],
"ldh_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.",
"protein_ratio": 0.5,
"pleural_ldh_u_l": 100,
"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",
"ldh_two_thirds_uln": 133.3
}
]
}
}Tags
x402
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