Light's Criteria for Pleural Effusion

Today at morning report we discussed the Light's Criteria.

Light's criteria for exudative effusion are any of
protein level pleural:serum over 0.5
LDH pleural:serum of over 0.6
pleural LDH over 2/3 upper limit of normal for serum

The combination of the three criteria has a higher sensitivity, but a lower specificity, than each individual criterion. Light's criteria are sensitive for exudate; may have transudates falsely called exudates. If clinical appearance suggests transudate but Light's criteria says exudate, measure albumin in serum vs. pleural fluid. If serum albumin is over 12 greater than pleural fluid almost all have transudative.

Our case had a bloody effusion, which narrows Ddx somewhat to cancer, PE, trauma, infection (inc. pneumonia, TB)

Here is a review of Pleural Effusion by Dr. Light himself!

*A large left sided pleural effusion as seen on an upright chest X-ray.