Background: Cystatin-C may serve as an early biomarker of renal injury, to identify and initiate timely management of acute kidney injury (AKI) in horses.
Objectives: To evaluate urinary concentrations of cystatin-C compared to serum creatinine, for the diagnosis of AKI in hospitalized horses. Animals: Prospective study of 50 horses without evidence of AKI at hospital admission, requiring treatment with nephrotoxic medications.
Methods: Blood and urine were collected at admission (T1), after 48 hours (T2) and 96 hours (T3) to determine serial serum creatinine concentrations, hematologic parameters, urine specific gravity and urine cystatin-C concentrations, expressed as uncorrected urine cystatin-C (uCys), concentrations corrected for urine creatinine [uCys:crea ratio] and as fractional excretion of cystatin-C [CysFx]). A diagnosis of AKI was based on a rise in creatinine ≥0.3 mg/dL within 48 hours, despite normovolemia. Cystatin-C was measured by commercial ELISA. Univariate and linear discriminant analyses with cross-validation assessed performance of cystatin-C as an AKI biomarker (P < 0.05 significant).
Results: Nine of 50 horses developed hospital-acquired AKI, and were compared to 16 of 41 hospitalized horses without AKI, based on matching sex, age, and reason for presentation. Neither uCys nor uCys:crea ratios were positively associated with AKI. However, 7 of 9 AKI patients showed a rise in CysFx (61.8±26.4%) at the time of diagnosis, which differed from non-AKI horses (P=0.009). An additional horse showed a 51.4% rise in CysFx 48 hours before developing AKI. Conclusions and Clinical Importance: AKI was associated with a rise in fractional excretion of cystatin-C in this population of hospitalized horses.
