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Reliability of using reagent test strips to estimate blood urea nitrogen concentration in dogs and cats

Allyson C. BerentDepartment of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.
Present address is the Matthew J. Ryan Veterinary Hospital of the University of Pennsylvania, Philadelphia, PA 19104.

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Tsuyoshi MurakamiDepartment of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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Richard D. ScrogginDepartment of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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Dori L. BorjessonDepartment of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

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Abstract

Objective—To evaluate the clinical accuracy of reagent test strips used to estimate BUN concentration in dogs and cats.

Design—Prospective study.

Animals—116 dogs and 58 cats.

Procedure—Blood samples were collected at the time of admission to the hospital. Estimates of BUN concentration obtained with reagent test strips (category 1 [5 to 15 mg/dL], 2 [15 to 26 mg/dL], 3 [30 to 40 mg/dL], or 4 [50 to 80 mg/dL]) were compared with SUN concentrations measured with an automated analyzer. For dogs, category 1 and 2 test strip results were considered a negative result (nonazotemic) and category 3 and 4 test strip results were considered a positive result (azotemic). For cats, category 1, 2, and 3 test strip results were considered a negative result (nonazotemic) and category 4 test strip results were considered a positive result (azotemic).

Results—On the basis of SUN concentration, 40 of the 174 (23%) animals (20 dogs and 20 cats) were classified as azotemic. One dog and 2 cats had falsenegative test strip results, and 1 dog had a false-positive result. Sensitivity and specificity were 95% (20/21) and 99% (94/95), respectively, for dogs and 87% (13/15) and 100% (43/43), respectively, for cats.

Conclusions and Clinical Relevance—Results suggest that reagent test strips are a reliable method for rapidly estimating BUN concentrations in dogs and cats. Because test strip results are only semiquantitative and there remains a potential for misclassification, especially in cats, urea nitrogen concentration should ultimately be verified by means of standard chemistry techniques. (J Am Vet Med Assoc 2005;227:1253–1256)

Abstract

Objective—To evaluate the clinical accuracy of reagent test strips used to estimate BUN concentration in dogs and cats.

Design—Prospective study.

Animals—116 dogs and 58 cats.

Procedure—Blood samples were collected at the time of admission to the hospital. Estimates of BUN concentration obtained with reagent test strips (category 1 [5 to 15 mg/dL], 2 [15 to 26 mg/dL], 3 [30 to 40 mg/dL], or 4 [50 to 80 mg/dL]) were compared with SUN concentrations measured with an automated analyzer. For dogs, category 1 and 2 test strip results were considered a negative result (nonazotemic) and category 3 and 4 test strip results were considered a positive result (azotemic). For cats, category 1, 2, and 3 test strip results were considered a negative result (nonazotemic) and category 4 test strip results were considered a positive result (azotemic).

Results—On the basis of SUN concentration, 40 of the 174 (23%) animals (20 dogs and 20 cats) were classified as azotemic. One dog and 2 cats had falsenegative test strip results, and 1 dog had a false-positive result. Sensitivity and specificity were 95% (20/21) and 99% (94/95), respectively, for dogs and 87% (13/15) and 100% (43/43), respectively, for cats.

Conclusions and Clinical Relevance—Results suggest that reagent test strips are a reliable method for rapidly estimating BUN concentrations in dogs and cats. Because test strip results are only semiquantitative and there remains a potential for misclassification, especially in cats, urea nitrogen concentration should ultimately be verified by means of standard chemistry techniques. (J Am Vet Med Assoc 2005;227:1253–1256)