Light's criteria for exudate being more likely than transudate

• The ratio of pleural fluid protein to serum protein is greater than 0.5
• The ratio of pleural fluid LDH and serum LDH is greater than 0.6
• Pleural fluid LDH is greater than 0.6 or 2/3 the upper normal limit for serum (Different labs have different upper normal limit but examples include 200 and 300 IU/L