Evaluation of serum gamma-glutamyltransferase activity as a predictor of passive transfer status in crias

OBJECTIVE: To determine the relationship between serum gamma-glutamyltransferase (GGT) activity and serum IgG concentration in neonatal crias. DESIGN: Prospective observational study. ANIMALS: 21 llama and 4 alpaca crias from 0 to 5 days old. PROCEDURE: Serum GGT activity was measured, using a commercially available kit. Serum IgG concentration was determined by use of radial immunodiffusion. With a serum IgG concentration of 1,000 mg/dl (considered adequate passive transfer), specificity and sensitivity of serum GGT activity in the detection of failure of passive transfer were determined. Regression models were developed to determine the relationship between serum GGT activity and serum IgG concentration. RESULTS: Sensitivity ranged from 0.56 to 0.89, and specificity ranged from 0.88 to 0.31, depending on the value of serum GGT activity chosen as a threshold. Proportion of crias correctly classified ranged from 0.76 to 0.52. Regression models failed to demonstrate a significant relationship between serum GGT activity and serum IgG concentration. CLINICAL IMPLICATIONS: Passive transfer status in crias cannot be accurately predicted on the basis of serum GGT activity.