Urinary cystatin B differentiates progressive versus stable IRIS Stage 1 chronic kidney disease in dogs

BACKGROUND

Early identification of dogs with progressive vs stable chronic kidney disease (CKD) might afford opportunity for interventions that would slow progression. However, currently no surrogate biomarker reliably predicts CKD progression.

HYPOTHESIS/OBJECTIVES

Urinary cystatin B (uCysB), a novel kidney injury biomarker, predicts progressive disease in International Renal Interest Society (IRIS) CKD Stage 1.

ANIMALS

Seventy-two dogs, including 20 dogs from 4 university centers with IRIS CKD Stage 1, with IDEXX symmetric dimethylarginine (SDMA) concentration up to 17 μg/dL and no systemic comorbidities, and 52 clinically healthy staff-owned dogs from a fifth university center.

METHODS

A multicenter prospective longitudinal study was conducted between 2016 and 2021 to assess uCysB concentration in IRIS CKD Stage 1 and control dogs. Dogs were followed to a maximum of 3 years (control) or 25 months (CKD). Stage 1 IRIS CKD was classified as stable or progressive using the slope of 1/SDMA, calculated from 3 timepoints during the initial 90-day period. Dogs with slope above or below -0.0007 week × dL/μg were classified as stable or progressive, respectively. Mixed effects modeling was used to assess the association between uCysB and progression rate.

RESULTS

Estimates of first visit uCysB results predictive of active ongoing kidney injury based on the mixed effects models were 17 ng/mL for control, 24 ng/mL for stable CKD, and 212 ng/mL for progressive CKD (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Urinary cystatin B differentiated stable vs progressive IRIS CKD Stage 1. Identification of dogs with progressive CKD may provide an opportunity for clinicians to intervene early and slow progression rate.

Urinary clusterin and cystatin B as biomarkers of tubular injury in dogs following envenomation by the European adder

Diagnosing acute kidney injury remains a challenge since the established renal biomarkers, serum creatinine (sCr) and symmetric dimethylarginine (SDMA) reflect glomerular function and not tubular injury. Sensitive tubular markers such as urinary clusterin (uClust) and cystatin B (uCysB) have been proposed to detect AKI at an earlier stage. Since envenomation by the European adder (Vipera berus berus) could serve as a spontaneous disease model of AKI we investigated these new biomarkers in affected dogs. Concentrations of uClust and uCysB as well as sCr and SDMA were analyzed retrospectively in stored samples from 26 dogs with snake envenomation and 13 healthy controls. Higher concentrations of uClust (P < 0.012) and uCysB (P < 0.001) were observed in the snake-envenomed group. Normalization of uClust and uCysB to urinary creatinine did not alter the results. No differences were observed in sCr and SDMA between the snake-envenomed group and the healthy control group. Spearman rank correlation analysis revealed a strong association of uClust with uCysB in the snake-envenomed dogs (r = 0.75 P < 0.001) but not in the healthy controls. The high percentage of snake-envenomed dogs with increased uClust and uCysB concentrations in the absence of increased sCr and SDMA suggests renal tubular injury in the affected dogs. Larger prospective case-controlled studies are warranted to evaluate the clinical utility and prognostic value of these biomarkers.

Measurements of echocardiographic indices and biomarkers of kidney injury in dogs with chronic kidney disease

Pathophysiological cardiac and renal interactions are termed cardiovascular-renal disorder (CvRD). Cardiovascular disease/dysfunction secondary to kidney disease (CvRD_K), is a leading cause of death in human chronic kidney disease (CKD) patients. The presence and clinical impact of CvRD_K in dogs with CKD is unknown. We hypothesized that echocardiographic measurements, and cardiac and renal biomarkers, will be altered in dogs with CKD and associated with survival. Eleven dogs with CKD (n = 6 IRIS stage 2, n = 5 IRIS stage 3) and without primary cardiac disease, plus 12 healthy age-matched control dogs, were recruited to this prospective observational study. Dogs underwent standard echocardiography, glomerular filtration rate (GFR) estimation by iohexol clearance, and measurement of plasma cardiac troponin I and N-terminal pro-B-type natriuretic peptide (NT-proBNP), plasma and urinary cystatin B, and urinary clusterin and neutrophil gelatinase-associated lipocalin (NGAL). Values were compared between groups, and their association with all-cause mortality explored. Dogs with CKD had significantly lower GFR and higher NT-proBNP, urinary cystatin B, clusterin, and NGAL, compared to controls (P < 0.05). Echocardiographic measurements were similar between dogs with CKD and controls. Median follow-up time was 666 days, during which six dogs with CKD died. Risk of death was associated with increasing age, serum total protein, and normalized left ventricular posterior wall thickness (LVPWDN) and decreasing bodyweight and packed cell volume. Although baseline differences in echocardiographic measurements were not evident between dogs with moderate CKD and controls, the presence of CvRD_K was suggested by the association between LVPWDN and survival.