Evaluation of specific biomarkers in blood serum and effusion fluids in determining glycocalyx damage in cats with feline infectious peritonitis

The aim of this study was to evaluate glycocalyx damage using some specific endothelial glycocalyx biomarkers in blood serum and pleural fluid of cats with suspected effusive FIP. The animal material of the study consisted of a total of 50 cats of different breeds, ages and sexes, 40 cats diagnosed with suspected FIP (FIP group) and 10 healthy cats (control group), which were admitted to the clinics of the Department of Internal Medicine, Animal Hospital, Faculty of Veterinary Medicine, Selcuk University for diagnosis, treatment and control purposes. The age of the cats ranged from 3 months to 4 years. A diagnosis of suspected FIP was made in cats with symptoms consistent with effusive FIP (pleural/peritoneal effusion), a positive feline coronavirus Ag test, an A:G ratio <0.45, a total protein (TP) concentration in the effusion fluid > 3.5 g/dL, a nucleated cell count <1000 per millimetre and a positive Rivalta test result. Alpha-1-acid glycoprotein (AGP), syndecan-1 (Syn-1) and chondratin sulphate (CS) concentrations were measured with cat-specific and claudin-5 (CL-5) concentrations were measured with universal commercial ELISA kits in blood serum and pleural fluid samples (FIP group). Serum AGP, Syn-1 and CS concentrations were significantly higher (p=0.000) and CL-5 concentrations were significantly lower (p=0.005) in cats with suspected effusion FIP compared to healthy cats. AGP, Syn-1 and CS concentrations were also found to be high in the blood serum of cats with suspected effusive FIP. Endothelial glycocalyx biomarkers showed significant correlations with each other and with hematological parameters. Albumin levels were negatively correlated with Syn-1 and CS concentrations and the A:G ratio was negatively correlated with AGP, Syn-1 and CS concentrations in cats with suspected effusive FIP. A WBC cut-off value of 12.40 (cells/ml), a Syn-1 cut-off value of 2.11 ng/ml and a CS cut-off value of 29.14 were found to be important indicators for prognosis and prediction of mortality in cats with suspected effusive FIP. In conclusion, the significant increase in the concentrations of Syn-1 and CS, components of the endothelial glycocalyx, in cats with suspected effusive FIP is associated with damage to the endothelial glycocalyx and is thought to be related to effusion in the pathogenesis of FIP disease.