Comparison between ultrasound and genetic testing for the early diagnosis of polycystic kidney disease in Persian and Exotic Shorthair cats

Autosomal-dominant polycystic kidney disease (AD-PKD) is common in Persians and Persians-related breeds. The aims of this study were to evaluate the sensitivity and specificity of early ultrasound examination and to compare ultrasound and genetic testing for early diagnosis. Sixty-three Persians and seven Exotic Shorthairs were considered. All underwent ultrasonographic and genetic testing (polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) assay) between 2.5 and 3.5 months of age (10-14 weeks). With ultrasound, 41.4% showed renal cysts, while 37.1% were PKD positive by genetic testing and DNA sequencing. Six cats with at least one renal cyst were negative by genetic testing, while only one cat negative at ultrasound resulted positive at genetic test. DNA sequencing of three polycystic cats, negative by genetic test, revealed they were heterozygous for the mutation. Agreement was described by Cohen's kappa that resulted 0.85, considering genetic test and DNA sequencing. Sensitivity and specificity of ultrasound were 96.2% and 91%, respectively. Sensitivity was higher and specificity lower than reported previously. The higher sensitivity could be due to improved technical capabilities of ultrasound machines and transducers. Other causes of PKD could explain the lower specificity. In conclusion, ultrasound resulted in a reliable diagnostic method for feline AD-PKD1 at early age and it should always be used with genetic testing, in order to reach a complete screening programme and eventually to identify other genetic mutations.