Identification of contaminant interferences which cause positive urine reagent test strip reactions in a cage setting for the laboratory‐housed nonhuman primate, Beagle dog, and Sprague–Dawley rat

Abstract

Background A high incidence of unexplained positive urine reagent test strip reactions was observed in healthy, untreated laboratory‐housed nonhuman primates, Beagle dogs, and Sprague–Dawley rats. Exposure of urine to cage pan contaminants was the suspected cause of the positive reactions. Objectives The objective of this study was to identify cage pan contaminants which could cause positive reagent test strip reactions. Methods Contaminated urine was simulated by exposing water samples to cage pan contaminants, including cleaning solutions, feces from nonhuman primates, Beagle dogs, and Sprague–Dawley rats, certified laboratory animal diets, and dietary enrichments (vegetables, fruits, and food treats). Ten samples were prepared for each contaminant and analyzed for blood, glucose, bilirubin, ketones, pH, protein, urobilinogen, nitrite, and leukocyte esterase using commercially available urine reagent test strips and an automated urine chemistry analyzer. Results Positive reactions were common for all but one analyte and frequently associated with multiple contaminants. Blood, glucose, and protein reactions had the highest incidence and/or strongest positive reactions. Positive reactions for other reagent test strip analytes were observed, but generally of lower incidence and magnitude. Conclusions We identified a high incidence of contaminant interferences in a water matrix causing positive reagent test strip reactions, primarily for the blood, glucose, and protein reactions. These findings highlight the potential limited value of urine reagent test strip assays as reliable biomarkers for detecting kidney toxicity in nonclinical studies, and imply that urine collection methods that minimize exposure to contaminants will likely improve the diagnostic validity of reagent test strip assays.

Influence of preanalytical factors on feline proteinuria

“…For example, feces or detergent contamination could occur and, in turn, affect urinalysis. 18 Furthermore, a delay in collecting urine from the litter (over 1 hour) could have resulted in a marked evaporation of the specimen and an alteration in the UPC. However, evaporation would more likely have a major effect on UP and UC concentrations and less of an effect on the UPC ratios, given the similar theoretical concentrating effects on proteins and creatinine (both of which are not volatile compounds at room temperature).…”

Noninvasive sampling method for urinalysis and urine protein profile in captive giraffes

“…6,23 In addition, contamination with non-protein compounds, such as non-protein pigments deriving from a vegetable-based diet, could also cause a positive reaction. 4,23,30,34,39 As a result, the positive values for dipstick proteins should be carefully considered and compared with uTP and UPC values determined by quantitative methods. 34 Given that UPC values of giraffes were lower than the threshold established for domestic species, these specimens might be considered non-proteinuric and the protein dipstick findings a false-positive result.…”

“…However, the dipstick nitrite positivity might also be affected by a vegetarian diet, and is not reported typically in veterinary medicine. 34,39 Urine dipsticks are considered reliable for urine pH, glucose, ketones, bilirubin, occult blood, and protein. Consequently, the dipstick WBC positivity might be considered an unreliable result, also in light of the subsequent negative sediment analysis.…”

Application of leukocyte esterase strip test in the screening of periprosthetic joint infections and prospects of high-precision strips

“…(1) the effect of different products of LE strips or test equipment on the results [30], 2) the influence of confounding factors, for example, blood, in the interpretation of strip test results, may cause discontinuities in the research queue [51], 3) the potential impact of test time point and sample size on the test results [29].…”

“…However, the controversy surrounding this diagnostic criterion lingers [ 8 ]. Regarding the strip test, the disagreement mainly focuses on the following aspects: (1) the effect of different products of LE strips or test equipment on the results [ 30 ], 2) the influence of confounding factors, for example, blood, in the interpretation of strip test results, may cause discontinuities in the research queue [ 51 ], 3) the potential impact of test time point and sample size on the test results [ 29 ].…”