Urinary carboxylesterase 5A fragment as an early diagnostic marker of cat chronic kidney disease

SUMMARY Chronic kidney disease (CKD) is a common disorder and cause of death in cats. In the classification proposed by the International Renal Interest Society (IRIS), stage I and II CKD are difficult to diagnose accurately using markers, in comparison with normal controls. We recently described a simple and highly reproducible two-step method for identifying potential disease-marker candidates among low-abundance urine proteins. Urine samples were taken from 56 normal control cats as the control group and from 56 cats with CKD (stage I). A carboxylesterase 5A fragment and filaggrin-2 fragment were identified as two proteins with higher levels in normal control cats. The performance of the ELISA of urine carboxylesterase 5A fragment was satisfactory in terms of recovery (97.2–102.4%) and within-run (1.3–3.6%) and between-day (1.5–4.1%) reproducibility. Urine carboxylesterase 5A fragment levels were significantly greater in normal cats (3.4±0.6 mg/dL) than in CKD (stage I) (1.9±0.5 mg/dL) (p<0.001). A carboxylesterase 5A fragment may be useful as a complementary marker to P-Cre and BUN for detection of CKD (stage I).