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Discriminating transudates and exudates in dogs with pleural effusion: diagnostic utility of simplified Light’s criteria compared with traditional veterinary classification
  1. Andrea Zoia1,
  2. Matteo Petini1,
  3. Danila Righetti1,
  4. Marco Caldin2 and
  5. Michele Drigo3
  1. 1Division of Internal Medicine, San Marco Veterinary Clinic, Veggiano, Padova, Italy
  2. 2Division of Clinical Pathology, Laboratorio d’Analisi Veterinarie San Marco, Veggiano, Padova, Italy
  3. 3Department of Animal Medicine, Production and Health, University of Padua, Padua, Italy
  1. Correspondence to Dr Andrea Zoia, Division of Internal Medicine, San Marco Veterinary Clinic, 35030 Veggiano, Italy; zoia.andrea06{at}


Objectives To determine whether the simplified Light’s criteria (ie, pleural effusion lactate dehydrogenase concentration and serum total protein) can identify the pathophysiology of pleural effusion formation in dogs, and to assess whether these criteria were more accurate than the traditional veterinary classification based on pleural effusion total protein (TPp) and nucleated cell count (TNCCp).

Methods This is a cross-sectional study including 100 dogs with pleural effusion. The aetiology of effusion was used to classify the pathophysiology of its formation. Parameters measured included the simplified Light’s criteria, TPp and TNCCp. The diagnostic utility of the two methods in classifying pleural effusion formation was evaluated.

Results Seven transudates due to decreased colloid osmotic pressure, 18 transudates due to increased hydrostatic pressure gradient and 75 exudates were included in the study. The simplified Light’s criteria misclassified 2 of 75 exudates (98 per cent overall accuracy). The traditional veterinary classification scheme misclassified 31 of 75 exudates and 12 of 18 increased hydrostatic pressure gradient transudates (57 per cent overall accuracy). The frequency of agreement between the simplified Light’s criteria and the traditional veterinary classification with the true nature of the pleural effusion was significantly different (P<0.001).

Clinical significance The simplified Light’s criteria were highly accurate in discriminating exudates from transudates, while TPp and TNCCp had no diagnostic value in doing so.

  • pleural effusion
  • canine
  • lactate dehydrogenase
  • light's criteria
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  • Presented at the 27th ECVIM-CA Congress, St. Julian’s, Malta, September 2017

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Ethics approval All procedures complied with the European legislation ‘on the protection of animals used for scientific purposes’ (Directive 2010/63/EU) and with the ethical requirements of Italian law (Decreto Legislativo 04/03/2014, n 26). Accordingly, this study did not require an authorisation or an ID protocol number. Informed written consent was obtained from all dog owners.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available upon reasonable request. All data relevant to the study are included in the article or uploaded as supplementary information. The original data (ie, medical records) contain sensitive information that for 'privacy policy' cannot be made public without owner consent. Nevertheless, the authors have no restriction to share a minimal anonymised data set necessary to replicate study findings, which has been uploaded as 'supplementary material'.

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