Development and application of a scoring system for prognostic evaluation of equine liver biopsies.

REASONS FOR PERFORMING STUDY

The study was designed to investigate the prognostic value of liver biopsy during investigation of cases of suspected liver disease in mature horses.

HYPOTHESIS

That liver biopsy is the most prognostically useful technique in common usage in the investigation of suspected liver disease.

METHODS

This study examined the prognostic value of liver biopsy during the investigation of suspected liver disease in 73 mature horses. Histopathological variables comprising fibrosis, irreversible cytopathology, inflammatory infiltration, haemosiderin accumulation and biliary hyperplasia were found to be significant predictors of nonsurvival and were used to formulate a weighted biopsy score representing a prognostically useful broad comparative index of histopathological severity. Minimum and maximum possible scores were 0 and 14 points, respectively.

RESULTS

Retrospective application of the biopsy scoring system to the study population indicated that horses with scores of 0 or 1 were equally likely to survive to 6 months with a combined mortality of 4%. Horses with biopsy scores between 2 and 6 had a combined mortality of 33% and were at a 12-fold increased risk of nonsurvival within 6 months (hazard ratio = 12.04, 95% CI 134-107.81, P = 0.026) compared to horses with a biopsy score of 0. Horses with biopsy scores between 7 and 14 had a combined mortality of 86% and were at a 46-fold increased risk of nonsurvival (hazard ratio = 46.01, 95% CI 5.92-357.5, P < 0.001) compared to horses with biopsy score 0.

CONCLUSIONS

Application of the biopsy scoring system to histopathological findings in liver biopsy specimens was very useful in predicting survival of cases of suspected liver disease.

POTENTIAL RELEVANCE

Application of the findings in this study may not be directly applicable to other case populations. However, liver biopsy appears to be the most valuable prognostic technique employed during the investigation of suspected cases of liver disease in mature horses.