Prognostic value of serum cystatin C concentration in dogs with myxomatous mitral valve disease

BACKGROUND: Impaired renal function is 1 of the poor prognostic factors in dogs with myxomatous mitral valve disease (MMVD). However, the value of cystatin C (Cys‐C), a marker of renal function, as a prognostic marker for MMVD in dogs has not yet been explored. OBJECTIVE: This study aims to investigate the prognostic value of Cys‐C in dogs with MMVD. ANIMALS: Fifty client‐owned small‐breed dogs with MMVD were included in this study. METHODS: This is a retrospective, cross‐sectional study. The prognostic value of serum Cys‐C concentration was assessed using univariable and multivariable Cox hazard regression analyses. Kaplan‐Meier survival curves for MMVD‐specific survival in dogs stratified into high and low Cys‐C groups were generated and analyzed using the log‐rank test. RESULTS: Serum Cys‐C concentrations were significantly associated with MMVD‐related death (P < .01) in both univariable (hazard ratio [HR], 5.086; 95% confidence interval [CI], 1.950‐13.270) and multivariable Cox hazard regression analysis (HR, 4.657; 95% CI, 1.767‐12.270). The high Cys‐C group (n = 14) had a significantly shorter MMVD‐specific survival time than the low Cys‐C group (n = 36; P < .01). In dogs with normal blood creatinine concentrations, the high Cys‐C group (n = 10) had a significantly shorter MMVD‐specific survival time than the low Cys‐C group (n = 36; P < .01). CONCLUSIONS AND CLINICAL IMPORTANCE: High serum Cys‐C concentrations were associated with a worse prognosis of MMVD. Furthermore, serum Cys‐C could be a predictor of MMVD prognosis even in dogs with normal blood creatinine concentration.