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Calculator: Clinical criteria for exudative pleural effusion in adults (Light’s criteria with continuous likelihood ratios)

Calculator: Clinical criteria for exudative pleural effusion in adults (Light’s criteria with continuous likelihood ratios)

Pleural fluid protein  
Serum protein  
Pleural fluid LDH  
Serum LDH  
Upper limit of normal serum LDH  
Pre-test suspicion of an exudative effusion   %

Important: Inputs must be complete to perform calculation.

Pleural fluid to serum protein ratio  
Pleural fluid to serum LDH ratio  
Pleural fluid LDH to upper limit of normal serum LDH ratio  
Pre-test odds  
Pro ratio LR  
LDH ratio LR  
LDH proportion of lab limit LR  
Post-test odds  

Post-test probability   %
Decimal precision  


  • Please refer to UpToDate topic review on evaluation of pleural effusions for more information.
  • LDH: lactate dehydrogenase; LR: likelihood ratio; Pro Ratio; protein ratio; PFL: pleural fluid LDH; ULN: upper limit of normal ; SL: serum LDH.

Equations used
Pleural_fluid_to_serum_protein_ratio = Pleural_fluid_protein / Serum_protein
Pleural_fluid_to_serum_LDH_ratio = Pleural_fluid_LDH / Serum_LDH
PFL_to_UNL_SL_ratio = PFL / ULN_SL
Pre-test odds = (Pre-test suspicion of an exudative effusion / 100) / (1 - (Pre-test suspicion of an exudative effusion/100))
Pro_ratio_LR = e(13.46*(Pleural_fluid_to_serum_protein_ratio-0.503))
LDH_ratio_LR = e(6.59*(Pleural_fluid_to_serum_LDH_ratio-0.731))
LDH_proportion_of_lab_limit_LR = e(3.83*(PFL_to_UNL_SL_ratio-0.594))
Post-test odds = Pre-test odds * Pro_ratio_LR * LDH_ratio_LR * LDH_proportion_of_lab_limit_LR
Post-test probability = 100 * Post-test odds / (1 + Post-test odds)


Only digits 0 to 9 and a single decimal point (".") are acceptable as numeric inputs. Attempted input of other characters into a numeric field may lead to an incorrect result.

Information on this page may not appear correctly if printed.

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Topic 139614 Version 1.0