Objective: To establish reference intervals for plasma glutamate dehydrogenase (GLDH) in clinically healthy African penguins and 2) to investigate GLDH activities in antemortem plasma from birds with confirmed liver disease postmortem.
Methods: In this observational case-control study, the histopathological reports of all penguins (n = 12) at one zoological institution were reviewed over a 19-year period to identify birds with liver disease. A single archived plasma sample was evaluated for each of the clinically healthy birds, and 2 to 4 different time points of archived plasma samples were evaluated from the birds with liver disease.
Results: The prevalence of liver disease was 58% (7/12). Histopathological findings included hemosiderosis (n = 4; 3 mild, 1 severe), hepatitis (2), metastatic neoplasia (2; melanoma, proventriculus carcinoma), hepatic necrosis (2), and lymphoplasmacytic infiltrates (1). In 29 clinically healthy penguins, GLDH ranged from 0 to 12.14 U/L (mean, 6.01; reference interval, 0 to 13.55 U/L) without any effects from sex, age, or weight. The 4 birds with liver disease that exceeded normal GLDH activities included metastatic melanoma, necrotizing and heterophilic hepatitis, mild hepatic necrosis with sinusoidal yolk emboli and severe hemosiderosis, and severe hepatic necrosis. Glutamate dehydrogenase had positive correlations with ALT and AST in birds with liver disease.
Conclusions: Glutamate dehydrogenase appears to be a clinically useful predictor of liver disease in avians as in mammals. However, this liver biomarker is able to rule in liver disease, although it cannot definitively rule it out.
Clinical relevance: These data serve to advance the understanding of noninvasive diagnosis of liver disease in penguins, which may ultimately contribute to the advancement of care and conservation of this at-risk species.
Keywords: avian; enzymes; hepatic; pathology; plasma chemistry.