Diagnostic assessment of liver enzymes in blood profiles from dairy cows

Objective. The aim of this study was to establish the association, sensibility (Se) and specificity (Sp) of the plasmatic activity of glutamate dehydrogenase (GDH, EC: 1.4.1.3), aspartate aminotransferase (AST, EC: 2.6.1.1) and g?glutamil transpeptidase (GGT, EC: 2.3.2.2) as liver damage markers in blood profiles of dairy cows. Materials and methods. The records of the plasma activity for GDH, AST and GGT obtained from blood profiles taken from 1566 cows from 112 dairy herds. The association between enzymatic activity, area below the curve (ABC), and Se and Sp using a ROC curve were determined, considering liver damage when GDH >30 U/L or GGT >39 U/L. Results. The AST was more likely associated to GDH (r=0.55) than to GGT (r=0.44). AST also had a higher ABC (p=0.01) when using GDH >30 U/L as an indicator of liver damage. The correlation between AST and GGT was of r=0.42. AST Se to detect liver damage with a cut?off level of >150 U/L was lower than the Se of GGT. The critical point for maximum Se and Sp of the ROC curve was obtained with AST>110 U/L and an increase in the diagnostic concordance with GDH (Kappa>0.300), was obtained using this value. Conclusions. Plasma activity of AST is more associated to GDH than to GGT in dairy cows. The cut?off level of plasma activity of AST for liver damage prediction in dairy cows would be >110 U/L.