Analytical validation and reference intervals for a commercial multiplex assay to measure five novel biomarkers for acute kidney injury in canine urine

Exploring urinary biomarkers of early acute kidney injury in a clinical model of canine intraoperative hypotension: an observational cohort study

OBJECTIVE

To explore changes in urinary biomarkers of acute kidney injury (AKI) in healthy dogs experiencing intraoperative hypotension and explore the relationship between blood pressure and urinary biomarkers.

STUDY DESIGN

Observational cohort study.

ANIMALS

A group of 50 client-owned dogs.

METHODS

Urine and blood samples were collected prior to anaesthesia (T0), within 24 hours after anaesthesia (T1) and 10 days post-surgery (T10). During anaesthesia, the lowest mean arterial pressure (MAP) in each dog was identified. Impact of duration was explored by categorizing according to arbitrary thresholds of MAP < 50, < 60, < 70 and < 80 mmHg and calculating duration (minutes) within each category. Serum creatinine (Cr) and validated biomarkers of AKI including urinary gamma-glutamyl transferase (uGGT), urinary neutrophil gelatinase-associated lipocalin (uNGAL) and urinary cystatin C (uCystatin C) were measured. Biomarker measurements were standardized to urinary Cr. The frequency of dogs with proportional increases between T1 and T0 and between T10 and T0 was recorded. Multiple regression analysis determined the simplest subset of independent variables (lowest MAP, duration with each MAP category) to best explain the variance in the proportional change of each biomarker.

RESULTS

Hypotension, defined as MAP < 60 mmHg, was observed in 38/50 (76%) of the dogs. Between T1 and T0, increases in uGGT/Cr, uCystatin C/Cr and uNGAL/Cr were observed in 37 (82%), 17 (41 %) and 19 (35%) of 50 dogs, respectively. Of the variance observed in uGGT/Cr at T1/T0, 62% could be explained by the lowest MAP recorded when combined with duration MAP < 50 mmHg (adjusted R2 0.62).

CONCLUSIONS AND CLINICAL RELEVANCE

In this clinical model of intraoperative hypotension, uGGT/Cr demonstrated potential for diagnosis of early AKI. The use of other validated biomarkers of AKI requires further investigation to establish their clinical relevance in diagnosis of post-anaesthetic kidney injury.

The Use of Biomarkers to Track and Treat Critical Illness

Biomarkers are objectively measurable parameters that provide clinicians with timely information to guide diagnosis and patient management beyond that which can be obtained from routinely available data. The literature contains thousands of articles on biomarkers in veterinary medicine. Specifically reviewed are the acute kidney injury markers neutrophil gelatinase-associated lipocalin, cystatin, clusterin, and kidney-injury molecule-1; the cardiac troponins and natriuretic peptides as biomarkers of heart disease; the acute phase protein C-reactive protein; procalcitonin; inflammatory cytokines; the markers of neutrophil extracellular trap formation cell-free DNA and nucleosomes; and markers of injury to the endothelium and endothelial glycocalyx including hyaluronan.

Urine Neutrophil Gelatinase-Associated Lipocalin in Non-Associative Immune Mediated Hemolytic Anemia: A Prospective Controlled Study in 22 Dogs

BACKGROUND

Urine neutrophil gelatinase-associated lipocalin (uNGAL) is a biomarker for the early diagnosis of AKI.

OBJECTIVES

To evaluate uNGAL in dogs with non-associative immune mediated hemolytic anemia (IMHA) and to evaluate whether uNGAL correlates with disease severity markers, negative prognostic indicators and outcome.

ANIMALS

Twenty-two dogs with non-associative IMHA and 14 healthy dogs.

METHODS

Prospective case-control study. uNGAL was measured by a commercially available ELISA-kit and corrected to urine creatinine (uNGAL to creatinine ratio [UNCR]). uNGAL and UNCR of IMHA cases were compared to that of healthy dogs and the correlation with other clinicopathological markers was evaluated. uNGAL and UNCR were also compared between dogs with a CHAOS or ASA score < 3 and ≥ 3.

RESULTS

uNGAL and UNCR were significantly higher in dogs with IMHA when compared to healthy controls (uNGAL median 114.58 and 0.43 ng/mL, respectively, p < 0.001; UNCR median 174.87 and 0.13 ng/mg, respectively, p < 0.001). uNGAL and UNCR were moderately positively correlated with urea (p = 0.005, r = 0.58, 0.20-0.81 95% CI and p = 0.001, r = 0.64, 0.29-0.84 95% CI, respectively) and total bilirubin (p = 0.003, r = 0.60, 0.22-0.82 95% CI and p = 0.002, r = 0.62, 0.25-0.83 95% CI, respectively). These were also significantly higher in dogs with hemoglobinuria compared to those without (uNGAL: median 269 and 30.99 ng/mL, respectively, p < 0.001; UNCR: median 585.3 and 352 37.47 ng/mg, respectively, p < 0.001). There was no statistically significant difference in uNGAL or UNCR when assessing survival to discharge (p = 0.24 and p = 0.16, respectively, 95% CI).

CONCLUSIONS

This study suggests that renal injury might be underappreciated in dogs with IMHA.

Early Detection of Chronic Kidney Disease Using Plasma Neutrophil Gelatinase-Associated Lipocalin and Kidney Injury Molecule-1 in Small-Breed Dogs: A Retrospective Pilot Study

Multiple diagnostic modalities are urgently needed to identify early-stage kidney diseases. Various molecules have been investigated; however, most studies have focused on identifying specific biomarkers in urine. Considering that assessing the symmetrical dimethylarginine (SDMA) plasma concentration is more suitable as an early diagnostic test for chronic kidney disease (CKD) in routine veterinary practice, we aimed to investigate the clinical usefulness of plasma neutrophil gelatinase-associated lipocalin (pNGAL) and plasma kidney injury molecule-1 (pKIM-1) concentrations for CKD detection in small-breed dogs. Through a retrospective analysis, we found that numerous clinicopathological data showed a log-normal distribution, even when they satisfied normality tests. Moreover, the log-transformed pNGAL and pKIM-1 concentrations successfully identified CKD International Renal Interest Society (IRIS) stages 1-4 and the risk group with underlying CKD risk factors. Correlation analysis and group comparison of other factors confirmed the possibility of using these two biomarkers for detecting the CKD risk group and IRIS stage 1. Receiver operating characteristic curve analysis revealed that the diagnostic accuracy for discriminating the risk group was superior in the order of pKIM-1, pNGAL, SDMA, and serum creatinine levels. In conclusion, these results suggest that pKIM-1 and pNGAL are possible early or quantifiable markers of insignificant CKD or can be at least used as an adjunct with traditional indicators.