Light's Criteria
Differentiates transudative from exudative pleural effusions to guide diagnostic workup
- Highest activation tier
- Mandatory
- How it is scored
- Scored in code; a detected disagreeing draft value is flagged for correction
- Scoring type
- classification
- Care settings
- Emergency department, ICU, Inpatient
When it activates
Scribeable activates a calculator from the encounter. The Light's Criteria can activate when the transcript or pasted chart context documents any of these:
- Pleural effusion characterization
- Thoracentesis result interpretation
- Exudative vs transudative differentiation
- New pleural effusion workup
A coded diagnosis can also activate it. ICD-10 prefixes carried by the registry: J90, J91.
Note-type scope: it activates on notes whose subject resolves to pulmonology, hospital medicine, emergency medicine, critical care. A note that resolves to another subject does not carry it even when the clinician's specialty matches; a note with no resolvable subject (a generic consultation) falls back to the specialty match.
Inputs the note needs
5 inputs. Each is resolved from the transcript, the pasted chart context and charted labs; an input marked "asks you" is requested as a clarification when it is undocumented.
| Input | Type | Unit / options | Guidance |
|---|---|---|---|
| Pleural fluid protein (g/dL) | lab | ||
| Serum protein (g/dL) | lab | ||
| Pleural fluid LDH (U/L) | lab | ||
| Serum LDH (U/L) | lab | ||
| Upper limit of normal for serum LDHoptional | lab |
Scoring
Exudate if ANY: (1) Pleural protein/serum protein >0.5, (2) Pleural LDH/serum LDH >0.6, (3) Pleural LDH >2/3 upper normal serum LDH.
Interpretation
Exudate: infection (empyema, TB), malignancy, PE, collagen vascular disease, pancreatitis. Transudate: CHF, cirrhosis, nephrotic syndrome, PE. Note: ~25% CHF effusions mis-classified as exudate after diuresis (serum-effusion albumin gradient can clarify).
Evidence
Sources carried in Scribeable's citation registry for this calculator; guideline version: Light RW et al. 1972.
- Light RW et al. Pleural effusions: the diagnostic separation of transudates and exudates (Light's Criteria)Light et al. (Light's Criteria) 1972 · 1972 · link last verified 2026-03-28
How Scribeable handles it in the note
When an encounter activates the Light's Criteria at the mandatory tier, Scribeable resolves its inputs from the transcript, the pasted chart context and any charted labs, and asks you for a missing input you can supply before the note is finalised. Bedside-exam and separately ordered study values are not requested one input at a time; a calculator that carries a combined clarification question may still put that single question to you.
The score is computed in code from the resolved inputs, not recalled by the language model. If the draft states a Light's Criteria value that disagrees with the computed one, the disagreement is flagged to the second drafting pass, which is instructed to correct the score and its interpretation before you see the note.
Classified as a risk score: activated strictly, by a documented trigger, never by a permissive reading of the encounter.
See it activate on your own encounter
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