Prediction of inherited portosystemic shunts in Irish Wolfhounds on the basis of pedigree analysis.

OBJECTIVE: To test validity of prediction for inherited portosystemic shunts (PSS) in Irish Wolfhounds, using nonselective clinical findings and a computerized database containing 5-generation pedigrees. ANIMALS: 613 dogs in the first and 396 dogs in the second cohort. PROCEDURE: Preprandial venous ammonia concentration was measured at 6 to 8 weeks in all pups born between Jan 1, 1988 and Jan 1, 1997 Portosystemic shunts were confirmed in hyperammonemic pups, using radioisotope shunt index measurement, and diagnosis of shunting was confirmed at abdominal surgery or necropsy. Findings in dogs of the first cohort (born before Jan 1, 1992) were used to predict shunting in their offspring of the second cohort. Common ancestors of first-cohort dogs with shunts were tested for positive associations with the disease. Risk for a shunt in all second-cohort dogs was predicted on the basis of relatedness with founders and was compared with outcome of clinical screening. RESULTS: Prevalence of shunts in first and second cohorts was 3.1 and 2.3%, respectively. Fifteen highly related associated founders could be identified. Second-cohort dogs were classified into 6 groups of increasing predicted risk. Mean number of dogs per class was 60; number of clinically diagnosed cases ranged from 0 in the class with the lowest risk to 4 in the highest risk class. CONCLUSIONS: Genetic risk for reproducing a PSS in Irish Wolfhounds was accurate, using the described method. CLINICAL RELEVANCE: Risk estimation provides a tool for genetic counseling, does not require knowledge of the mode of inheritance, and may be valid for any inherited disease.