If any of the following conditions are met, it is an exudate, full of protein and turbid, unclear fluid. Think malignancy or certain infections.
Light’s Criteria
- Pleural fluid protein / serum protein > 0.5
- Pleural fluid LDH / serum LDH > 0.6
- Pleural fluid LDH > 2/3 x upper limit of normal serum LDH
Memory Aid
- Pleural
- Criterion 1 = protein
- Criterion 2 = LDH
- Criterion 3 = LDH again
- Increasing numbers
- 0.5
- 0.6
- 0.666666 to infinity
References
- MDCalc. (2018). Light’s Criteria for Exudative Effusions. [online] Available at: https://www.mdcalc.com/lights-criteria-exudative-effusions [Accessed 14 Sep. 2018].
- Exeter Clinical Laboratory International. (2018). Transudate or Exudate / Blood Sciences Test. [online] Available at: https://www.exeterlaboratory.com/test/transudate-or-exudate/ [Accessed 14 Sep. 2018].