Use of the AST to Platelet Ratio Index (APRI) as a Serum Biomarker of Canine Hepatic Fibrosis
J. Stone; C. Lamm; T. Parkin; R. Bell
Background
The aspartate aminotransferase (AST) to platelet ratio index (APRI) is used in human medicine as a predictor of the presence or absence of significant hepatic fibrosis in patients with chronic hepatopathies. The APRI provides a simple, non-invasive method of predicting fibrosis and reducing the need for liver biopsy in a substantial proportion of patients.
Objective
To evaluate the APRI as a predictor of hepatic fibrosis in dogs.
Methods
The records of 55 dogs which had a liver biopsy performed at the University of Glasgow Small Animal Hospital between October 2007 and February 2011 were reviewed. Patients were excluded for the following reasons; inadequate haematology and biochemistry blood results, undetectable platelet numbers, thrombocytosis not attributable to hepatic disease, or inability to locate the original histology slides. The AST and platelet values closest to the time of biopsy were used to calculate the APRI. The biopsy method (surgical, laparoscopic or Tru-cutTM needle) was recorded. All biopsies were reviewed and scored by a board-certified histopathologist who was blinded to the APRI, and attributed a score of 0–3 based on the degree of fibrosis, 0 being no fibrosis and 3 being severe fibrosis.
Kruskal-Wallis tests were performed to identify significant differences in APRI between dogs with differing fibrosis scores. Mann-Whitney tests were used to compare the APRI in dogs with a score of 0 to those with a score of 1 or more. This was done firstly for all dogs and secondly for those from which a surgical biopsy was obtained.
Results
Thirty two dogs were included in the analysis of which 26 had surgical, 4 had laparoscopic and 2 had Tru-cutTM biopsies. All dogs had haematology and biochemistry performed within 5 weeks prior to liver biopsy. Nineteen dogs had elevations in AST, 14 in alanine aminotransferase (ALT) and 21 in alkaline phosphatase (ALP).
Fibrosis scores of 0 (n = 11), 1 (n = 10), 2 (n = 3) and 3 (n = 8) were recorded.
The APRI was not significantly different between the fibrosis scores 1 to 3. However, the APRI was significantly different for dogs with (scores 1–3) and without (score 0) hepatic fibrosis (P-value = 0.002). Biopsy method did not impact on these results.
Conclusion
The APRI may be useful to predict the presence or absence of hepatic fibrosis in dogs undergoing investigations for liver disease.