Respiratory

Question 1

Lights Criteria

Answer 1

Pleural effusions may be exudates or transudates. The distinction is important for an accurate diagnosis and to help determine what further evaluations may be necessary. Lights criteria use ratios of fluid/serum values for protein and LDH. Pleural fluid/serum ratios greater than 0.6 for LDH and 0.5 for protein are indicative of exudates. In the scenario presented, both ratios are approximately 0.3; therefore, the fluid is a transudate. The list of causes for transudates is much shorter than for exudates. The vast majority of transudates are due to heart failure, with cirrhosis being the next most common cause.