Light's Criteria 

Updated: Aug 09, 2018
  • Author: James J Lamberg, DO; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Light's Criteria

Determination of transudate versus exudate source of pleural effusion

Fluid is exudate if one of the following Light’s criteria is present: [1, 2, 3, 4]

  • Effusion protein/serum protein ratio greater than 0.5

  • Effusion lactate dehydrogenase (LDH)/serum LDH ratio greater than 0.6

  • Effusion LDH level greater than two-thirds the upper limit of the laboratory's reference range of serum LDH

Exudative effusions

See the list below:

  • Abdominal fluid: Abscess in tissues near lung, ascites, Meigs syndrome, pancreatitis

  • Connective-tissue disease: Churg-Strauss disease, lupus, rheumatoid arthritis, Wegener granulomatosis

  • Endocrine: Hypothyroidism, ovarian hyperstimulation

  • Iatrogenic: Drug-induced, esophageal perforation, feeding tube in lung

  • Infectious: Abscess in tissues near lung, bacterial pneumonia, fungal disease, parasites, tuberculosis

  • Inflammatory: Acute respiratory distress syndrome (ARDS), asbestosis, pancreatitis, radiation, sarcoidosis, uremia

  • Lymphatic abnormalities: Chylothorax, malignancy, lymphangiectasia

  • Malignancy: Carcinoma, lymphoma, leukemia, mesothelioma, paraproteinemia

Transudative effusions

See the list below:

  • Atelectasis: Due to increased negative intrapleural pressure

  • Cerebrospinal fluid (CSF) leak into pleural space: Thoracic spine injury, ventriculoperitoneal (VP) shunt dysfunction

  • Heart failure

  • Hepatic hydrothorax

  • Hypoalbuminemia

  • Iatrogenic: Misplaced catheter into lung

  • Nephrotic syndrome

  • Peritoneal dialysis

  • Urinothorax: Due to obstructive uropathy

Exceptions

These are processes that typically cause exudative effusions, but may cause transudative effusions.

  • Amyloidosis

  • Chylothorax

  • Constrictive pericarditis

  • Hypothyroid pleural effusion

  • Malignancy

  • Pulmonary embolism

  • Sarcoidosis

  • Superior vena cava obstruction

  • Trapped lung

Leading causes of pleural effusion

See the list below:

  • Congestive heart failure (transudate), incidence 500,000/year

  • Pneumonia (exudate), incidence 300,000/year

  • Cancer (exudate), incidence 200,000/year

  • Pulmonary embolus (transudate or exudate), incidence 150,000/year

  • Viral disease (exudate), incidence 100,000/year

  • Coronary-artery bypass surgery (exudate), incidence 60,000/year

  • Cirrhosis with ascites (transudate), incidence 50,000/year

Test sensitivity and specificity for exudate

Table 1. Test Sensitivity and Specificity for Exudate (Open Table in a new window)

 

Sensitivity, %

Specificity, %

Light’s criteria

98

83

Protein/serum protein ratio >0.5

85

84

LDH/serum LDH ratio >0.6

90

82

LDH >2/3 upper limits of serum normal

82

89

Pleural-fluid cholesterol level >60 mg/dL

54

92

Pleural-fluid cholesterol level >43 mg/dL

75

80

Pleural-fluid/serum cholesterol ratio >0.3

89

81

Serum/pleural-fluid albumin level ≤1.2 g/dL

87

92

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