A new approach to pleural effusion in cats: Markers for distinguishing transudates from exudates

Abstract

Classification of pleural effusion (PE) is central to diagnosis. Traditional veterinary classification has distinguished between transudates, modified transudates and exudates. In human medicine PEs are divided into only two categories: transudates and exudates. The aim of this study was to evaluate, in 20 cats presented with PE, paired samples of serum and pleural fluid for the following parameters: Light's criteria (pleural fluid lactate dehydrogenase concentration (LDHp), pleural fluid/serum LDH ratio, pleural fluid/serum total protein ratio (TPr)), pleural fluid total protein, pleural fluid cholesterol concentration, pleural fluid/serum cholesterol ratio (CHOLr), serum-effusion cholesterol gradient (serum cholesterol minus PE cholesterol concentration (CHOLg)), PE total nucleated cells count (TNCCp) and pleural fluid glucose (GLUp). LDHp and TPr were found most reliable when distinguishing between transudates and exudates, with sensitivity of 100% and 91% and specificity of 100%, respectively. When conflict between the clinical picture and laboratory results exists, calculation of CHOLr, CHOLg and TNCCp measurement may help in the classification of the effusion. Measurement of serum albumin (in the case of a transudate) may provide additional information regarding the pathogenesis of the effusion.

An update on feline infectious peritonitis: Diagnostics and therapeutics

“…FIP fluids are frequently labeled 'modified transudates' based on their perceived lack of cellularity. However, they are inflammatory exudates in the purest sense and do not meet the established physical or physiologic criteria for a modified transudate (Zoia et al, 2009). Most FIP effusions contain a fair number of cells (500-5000/μL), including macrophages, neutrophils and a low proportion of lymphocytes.…”

A clinical review of the pathophysiology, diagnosis, and treatment of pyothorax in dogs and cats

“…Light's criteria have been evaluated in the classification of feline pleural effusion . In a recent prospective study, pleural fluid LDH and pleural fluid/serum total protein ratio were found to be the most sensitive and specific markers when classifying pleural fluid as a transudate or exudate, although pleural fluid pH was not measured . Biochemical markers of sepsis have also been evaluated in dogs and cats with peritoneal effusion.…”

Transudate or exudate: can lactate dehydrogenase activity in canine and feline effusions help to differentiate between the 2?

“…As many veterinary practices currently have dry chemistry analyzers available that are capable of measuring LDH activity, this analyte could be useful in practice, allowing early and more targeted treatment. Although some studies involving cats and dogs have already been published, a systematic, prospective study evaluating LDH activity (plus other criteria) in animal effusions, paying attention to the effects of testing interval, freezing, postmortem interval, and sample origin, has not been done.…”