Internal Medicine Clinical Criteria

Most commonly encountered criteria in internal medicine

Light's Criteria

Transudative vs exudative

Commonly encountered both clinically and on board exams, Light's criteria can be used to determine whether pleural fluid is transudative or exudative. Transudative fluid is more likely to be due to congestive heart failure, liver failure, or nephrotic syndrome (think decreased oncotic pressure). Exudative fluid will make you worried about malignancy, bleeding, or infection.

Example clinical situation: fluid analysis after thoracocentesis.

Criteria: for a fluid to be considered exudative, it needs to only meet one of the following:

  • Fluid LDH to serum LDH ratio >0.6
  • Fluid total protein to serum total protein ratio >0.5
  • Fluid LDH total value >2/3 of serum maximum

CHA2DS2-VASc Score

Atrial fibrillation

A very useful scoring system to estimate the probability of cardiac-origin stroke in patients with atrial fibrillation. The scoring system is also useful for deciding on the type of treatment those patients receive. The application of the CHA2DS2-VASc scoring system is commonly tested on board exams, but is equally useful on the ward.

Example clinical situation: patient with heart failure presents to his internist with newly discovered sustained atrial fibrillation

Criteria: higher scores indicate higher probability of stroke without treatment (up to 15.2% annual risk for max score of 9). Most guidelines generally recommend Aspirin for scores of 1, and anticoagulation with Vitamin K agonists for scores of 2 or more (or even 1 in males). The components of CHA2DS2-VASc are:

  • Congestive heart failure
  • Hypertension
  • Age≥75. Two points are given for this.
  • Diabetes
  • Stroke or TIA, or thromboembolism history. Two points are given for this.
  • Vascular disease
  • Age: 65-74
  • Sex: female gender

Winnipeg Criteria

COPD exacerbation

Perhaps encountered less commonly outside Canada, Winnipeg criteria help you determine whether a patient is presenting with an acute exacerbation of COPD (COPDE).

Example clinical situation: a known COPDer presenting with acute dyspnea and chest pain.

Criteria: an increase in one of the following cardinal symptoms in a patient known to have COPD should promote you to consider COPDE:

  • Shortness of breath, or
  • Sputum production, or
  • Change in sputum character

Well's Criteria


Developed in Ottawa, Well's criteria are often used to estimate the probability of deep vein thrombosis in the emergency department. Similar criteria exist for pulmonary embolism

Example clinical situation: leg swelling in a cancer patient.

Criteria: one point for each criterion present below. A score of 1-2 indicates moderate probability. A score of 3+ indicates high probability of DVT (between 17% and up to 53%).

  • Active cancer
  • Bedridden recently >3 days or major surgery within four weeks
  • Pitting edema only in the symptomatic leg
  • Calf asymmetry: unilateral swelling >3 cm relative to other leg
  • Collateral (nonvaricose) superficial veins present
  • Entire leg swollen
  • Localized tenderness along the deep venous system
  • Paralysis, paresis, or recent plaster immobilization of the lower extremity
  • Previously documented DVT
  • Alternative diagnosis to DVT as likely or more likely