N-acetyl-β-D-glucosaminidase in clinically healthy German Shepherd dogs and dogs with early stages of chronic kidney disease

Urinary N-acetyl-β-d-glucosaminidase (NAG) activity is associated with kidney disease. In our study, we focused on evaluating the ratio of NAG to the urinary creatinine concentration (NAG/Cr) in the German Shepherd breed. Sixty-two healthy dogs and thirteen dogs with chronic kidney disease (CKD) were examined. The healthy dogs were divided into groups based on their sex and age (puppies and adolescent dogs under 2 years, adult dogs from 2 to 6 years and seniors over 6 years), while the dogs with CKD were divided based on the disease stage (CKD stage 1 and 2). No significant difference was detected between the males and females. Regarding the age dependence, significantly higher values were found in dogs older than 6 years (P = 0.020 3) compared to dogs aged 2-6 years. When comparing the healthy dogs to the dogs with CKD, the lowest NAG/Cr ratio was observed in the dogs with CKD stage 2. The reference interval for NAG/Cr in the German Shepherd was established in the range of 0.78-7.86 U/gCr. We observed no correlations with the commonly used markers of kidney disease such as creatinine, urea, or symmetrical dimethylarginine. Nevertheless, we encourage the further investigation of NAG in relation to CKD, taking the breed, sex and age of the patients into account.