Screening for proteinuria in cats using a conventional dipstick test after removal of cauxin from urine with a Lens culinaris agglutinin lectin tip

[Urinalysis in dogs and cats, part 1: physical and chemical urinalysis]

The urinalysis of dogs and cats is an important part of the diagnostic evaluation of urinary tract diseases as well as for the identification of systemic diseases. A routine urinalysis consists of a physical and chemical examination of the urine as well as an examination of the urine sediment. Various urine collection methods (free-catch, catheterization, cystocentesis) are available. Each method has multiple advantages and disadvantages. The appropriate method must be chosen individually for each patient depending on the emphasis of the examination. The urine should ideally be examined within 30 minutes of collection as it is prone to change due to time and storage. Physical examination of the urine consists of the determination of urine color, clarity, and specific gravity which provides information regarding the concentration of the urine. The latter is determined by refractometry and needs to be interpreted in the context of the hydration status of the patient. Chemical examination of the urine consists of the determination of the pH value and the presence of blood/hemoglobin/myoglobin, protein, glucose, bilirubin, urobilinogen, nitrite, and ketones. The use of commercially available urine dipsticks is common. These must be stored and used according to the manufacturer's instructions and when interpreting the results, veterinary aspects need to be taken into consideration. The physical and chemical examinations of the urine represent rapid and readily performable methods that provide important information for the diagnosis or the exclusion of numerous diseases.

Leukocyte Esterase and Nitrite Urine Reagent Strip Utility Under Altered Assay Conditions in Dogs

The study evaluated leukocyte esterase (LE) and nitrite reagent pad usefulness in canine urine using multiple time endpoints and decision thresholds. Whole and sedimented urine samples from 116 client-owned dogs were analyzed with reagent strips from four manufacturers. Results for LE and nitrite were recorded every 30 s up to 150 s using "trace" and "+" positive thresholds and compared to microscopic urine sediment analysis and culture results. Sedimented urine assessed at 150 s with a "trace" positive threshold for LE had significantly or trending higher sensitivity (brand dependent) for pyuria detection compared with manufacturer recommendations. Using these parameters, LE sensitivity and negative likelihood ratio were 66.67-89.47%, and 0.13-0.37, respectively. Following manufacturer recommendations, LE specificity and positive likelihood ratio were 96.91-100% and 17.02-30.63, respectively. Nitrite performance for pyuria and bacteriuria detection was poor for all conditions. LE reagent pads are a useful screening test for pyuria detection using sedimented urine and a "trace" positive threshold at 150 s, whereas LE use with traditional manufacturer recommendations is a good confirmatory test for pyuria detection. Nitrite reagent pads are not useful for pyuria or bacteriuria detection.

Urinary Protein/Creatinine Ratio in Feline Medicine: Reasons to Perform It and Its Role in Clinical Practice-A Retrospective Study

This study aimed at understanding the reasons veterinarians conduct a urinary protein/creatinine ratio (UPCR) in cats, correlating it with signalment, dipstick proteinuria tests, and urine specific gravity (USG) and assessing its role in chronic kidney disease (CKD) diagnosis and monitoring. A retrospective study was conducted, including medical data from cats consulted between 2016 and 2018 in a veterinary teaching hospital and submitted to at least one UPCR measurement. A total of 140 cats were included: 35% non-proteinuric (UPCR < 0.2), 25% borderline proteinuric (0.2 < UPCR < 0.4), and 40% overtly proteinuric (UPCR > 0.4). In contrast to other studies, there was no association between UPCR and male reproductive status. UPCR was mainly requested for CKD diagnosis and monitoring. Correlation between UPCR and combined results from dipstick tests and USG was low and inconsistent. Proteinuric CKD cats had a worse outcome at both 6 (odds ratio (OR 4.04) and 12 months (OR 4.36)), and this finding was more pronounced for severely proteinuric cases in which the OR for death was 4.36 and 6.00 at 6 and at 12 months, respectively. In addition to reinforcing the negative prognostic value of proteinuria, this study stresses the low and the inconsistent agreement between UPCR and the combined results of dipstick tests and USG in cats.

Renal expression and urinary excretion of liver-type fatty acid-binding protein in cats with renal disease

Background

Liver‐type fatty acid‐binding protein (L‐FABP) is a biomarker for early detection of renal disease in humans. Liver‐type fatty acid‐binding protein is cytotoxic oxidation products secreted from proximal tubules under ischemia and oxidative stress.

Objective

To examine renal expression and quantify urinary excretion of L‐FABP in catswith renal disease.

Animals

One hundred and thirty‐four client‐owned cats including 34 cats with serum creatinine (sCre) values >1.6 mg/dL and 10 other cats that died in clinics.

Methods

Tissue expressions of L‐FABP were examined by reverse transcription polymerase chain reaction and Western blotting. Urinary L‐FABP (uL‐FABP) and serum L‐FABP (sL‐FABP) levels were determined by enzyme‐linked immunosorbent assay. Anti‐liver‐type fatty acid‐binding protein antibody immunostained renal sections.

Results

Feline kidneys express L‐FABP. Strong L‐FABP signals were observed in the lumens of proximal tubular cells in 5 cats with high uL‐FABP excretion, but not in 5 cats with low uL‐FABP excretion. In 9 normal cats, uL‐FABP index was <1.2 μg/g urinary creatinine (uCre). High uL‐FABP indexes (>10.0 μg/g uCre) were detected in 7 of 100 cats with low sCre (<1.6 mg/dL) and 18 of 44 cats with high sCre (>1.6 mg/dL). There was a weak correlation between L‐FABP index and sCre, serum symmetric dimethylarginine (SDMA), or blood urea nitrogen (BUN), and these correlation coefficients were increased by analyzing only data of cats with sCre >1.6 mg/dL. There was a weak correlation between u L‐FABP index and sL‐FABP in all tested cats, but not in cats with high sCre.

Conclusions and Clinical Importance

This study demonstrates correlations between L‐FABP and current renal biomarkers for chronic kidney disease in cats, such as sCre and SDMA. Liver‐type fatty acid‐binding protein may be a potential biomarker to predict early pathophysiological events in feline kidneys.

Urinalysis and determination of the urine protein-to-creatinine ratio reference interval in healthy cows

Background

There are no reference intervals for urinalysis in cattle.

Hypothesis/Objectives

Characterize the urine of healthy cows, establish urine protein‐to‐creatinine ratio (UPC) reference intervals, and test possible differences among dairy and beef cattle, age groups, or stage of lactation.

Animals

Seventy‐seven dairy and 74 beef 2.5 to 17 year‐old cows of different breeds housed mainly in free stall.

Methods

In this prospective study, urine specimens were collected by catheterization. Complete urinalysis was performed within 1 hour including specific gravity, dipstick evaluation, visual urine pH evaluation with 0.3 pH unit graded strips, and microscopic evaluation of the sediment. Urinary protein and creatinine concentrations and protein electrophoresis were determined on frozen aliquots.

Results

Overall reference intervals were 1.020 to 1.045 for USG, 7.0 to 8.7 for pH, and 0.04 to 0.25 for UPC; because of differences in creatinine concentration, UPC was lower in beef (0.04‐0.14) than in dairy (0.05‐0.25) cows and in the latter in dry than lactating cows. With dipstick evaluation, most analytes were absent except for blood, ketone, and protein in 24.7, 16.0, and 64.7% of cases, respectively. Microscopic evaluation revealed less than 3 red blood cells, leukocytes, and epithelial cells in 84, 99.3, and 100% cows, respectively. No band was observed at electrophoresis, except in 1 case at MW ~66 000.

Conclusions and Clinical Importance

Creatininuria is higher in beef than dairy cows and proteinuria is likely more efficiently characterized by protein concentration than by UPC.

Validation of an electrophoretic method to detect albuminuria in cats

Objectives The aims of this study were to validate a semi-automated high-resolution electrophoretic technique to quantify urinary albumin in healthy and diseased cats, and to evaluate its diagnostic performance in cases of proteinuria and renal diseases. Methods Urine samples were collected from 88 cats (healthy; chronic kidney disease [CKD]; lower urinary tract disease [LUTD]; non-urinary tract diseases [OTHER]). Urine samples were routinely analysed and high-resolution electrophoresis (HRE) was performed. Within-assay and between-assay variability, linearity, accuracy, recovery and the lowest detectable and quantifiable bands were calculated. Receiver operating curve (ROC) analysis was also performed. Results All coefficients of variation were <10%, percentage recovery was between 97% and 109% with a high linearity (r = 0.99). HRE allowed the visualisation of a faint band of albumin and a diffused band between alpha and beta zones in healthy cats, while profiles from diseased cats were variable. Albumin (mg/dl) and urine albumin:creatinine ratio (UAC) were significantly ( P <0.05) different between healthy and diseased cats. After ROC analysis, UAC values of 0.035 and 0.074 had a high sensitivity and high specificity, respectively, to classify proteinuria and identify borderline proteinuric cats. Moreover, a UAC of 0.017 had a high sensitivity in distinguishing between healthy and diseased cats. However, UAC was not able to distinguish between renal (CKD) and non-renal diseases (LUTD/OTHER), probably owing to the pathophysiology of CKD in cats, which is characterised by low-grade proteinuria and less glomerular involvement than in dogs. Conclusions and relevance HRE is an accurate and precise method that could be used to measure albuminuria in cats. UAC was useful to correctly classify proteinuria and to discriminate between healthy and diseased cats. HRE might also provide additional information on urine proteins with a profile of all proteins (albumin and globulins) to aid clinicians in the diagnosis of diseases characterised by proteinuria.

Changes in serum and urine SAA concentrations and qualitative and quantitative proteinuria in Abyssinian cats with familial amyloidosis: a five-year longitudinal study (2009-2014)

BACKGROUND

Diagnosis of familial amyloidosis (FA) in Abyssinian cats usually is made on postmortem examination.

HYPOTHESIS/OBJECTIVES

Sequential analysis of serum SAA (sSAA), urinary SAA (uSAA), urinary protein:creatinine (UPC) ratio, or sodium-dodecylsulfate agarose gel electrophoresis (SDS-AGE) may facilitate early identification of cats with FA.

ANIMALS

Twenty-three Abyssinian cats belonging to cattery A or B (low and high prevalence of FA, respectively).

METHODS

Prospective longitudinal study using 109 blood and 100 urine samples collected over 4-year period every 4 months, if possible, or more frequently in case of illness. Cats that died during study were necropsied. Health status of live cats was checked 5 years after enrollment. Serum amyloid A (sSAA) and urinary SAA (uSAA) were measured using ELISA kit. The UPC ratio and SDS-AGE also was performed.

RESULTS

Familial amyloidosis was not identified in cattery A, whereas 7/14 cats from cattery B had FA. Serum amyloid A concentrations were not significantly different between cats in catteries A and B or between cats with or without FA, despite frequent peaks in cats from cattery B. Conversely, uSAA was significantly higher in cattery B, especially in the terminal phases of FA. Proteinuria occasionally was found in cats from both catteries, especially in those with FA. Urine protein electrophoresis identified mixed proteinuria only in cats with FA.

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum amyloid A and UPC ratio are not helpful for early identification of Abyssinian cats with FA. Conversely, increases in uSAA with or without mixed proteinuria may be found before onset of clinical signs in cats with FA.

Immobilization of an esterase inhibitor on a porous hollow-fiber membrane by radiation-induced graft polymerization for developing a diagnostic tool for feline kidney diseases

Removal of the major urinary protein, cauxin, a carboxylesterase, from cat urine is essential for distinguishing between physiological and abnormal proteinuria by a urine dipstick. We have previously developed a material for removing cauxin by using lens culinaris agglutinin (LCA) lectin which targets the N-linked oligosaccharides present in cauxin. To improve the affinity and specificity toward cauxin, we immobilized 1,1,1-trifluoro-3-(2-sulfanylethylsulfanyl) propane-2-one, an inhibitor of esterases, to a polymer chain grafted on to a porous hollow-fiber membrane by applying radiation-induced graft polymerization. Normal male urine was forced to permeate through the pores rimmed by the ligand-immobilized polymer chain. Cauxin could not be detected in the effluent from the membrane. The residence time of the urine across a membrane thickness of 1 mm was set at 7 s. The respective dynamic and equilibrium binding capacities of the membrane for cauxin were 2 and 3 mg/g. The developed cauxin-affinity membrane material was more effective for diagnosing cat kidney diseases than the LCA lectin tip.