Pulmonology

Light's Criteria

Distinguishes exudative from transudative effusions.

Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.

When to use

Use on pleural fluid to classify an effusion as exudate or transudate. An effusion is exudative if ANY criterion is met.

Why use

It is the standard test to classify pleural effusions and direct further work-up.

Advice

If exudative, investigate for causes such as infection, malignancy or PE. Light's criteria can occasionally misclassify a transudate as exudate (e.g. on diuretics).

Evidence & references

Light RW et al. Pleural effusions: the diagnostic separation of transudates and exudates. Ann Intern Med. 1972.

About the creator

Richard Light

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