Validation of IDEXX VetLab UA Analyzer and IDEXX UA Strips for ...

Validation of IDEXX VetLab ® UA Analyzer and IDEXX UAStrips for Veterinary SamplesW LePage; S Corey; T Hunt, PhD; P Wong, PhD; M Frye, DVMABSTRACT: To validate IDEXX UA Strips and the IDEXX VetLab ® UAAnalyzer for veterinary samples against the reference instrument: BayerCLINITEK Atlas ® 5001B (Elkhart, IN). 203 urine samples (115 canine, 66feline and 22 equine) were run on both systems. The agreement betweenthe reference, the IDEXX UA strips visual read and the IDEXX VetLab ® UAwas greater than 90%.INTRODUCTION: It is well established that urinalysisis a key component of the minimum diagnosticprofile for all sick patients, along with chemistry andhematology. There is also general consensus that aurinalysis should be conducted as close as possibleto the time of collection to increase the accuracy, thusmaking it an ideal in-house test. IDEXX UA Strips arethe only urine dipsticks validated for veterinary useon canine, feline, and equine urine. The strips can beread visually or with the IDEXX VetLab ® UA Analyzer.The objective of this study was to compare the IDEXXresults (visual and reader) to the reference instrument(Bayer Atlas).There are two types of results from a photometric test:quantitative and semi-quantitatitive. For quantitativetests such as blood glucose measurement meters,color development on the test area is directlyproportional to the concentration of the analyte in thesample due to test device design and concentrationcalculation algorithm (see figure A). For semiquantitativetests such as the urinalysis strip screeningtest, the development of the reaction color on the testpads is influenced by different variables, includingsample handling, composition of the urine sample,intrinsic urine color, urine density, and urine volume onthe test paper (see figure B). Although urine analyzersmeasure the color intensity of the test strip inreflectance units with high precision, they are not ableto eliminate all influences on the color developmentas described above. Therefore, the urine analyzerindicates measurement results only in concentrationranges (semi-quantitative) in contrast to glucosemeters or other instruments. Therefore, for this study,the acceptance criterion was that all compared testmethods must have > 85% agreement of resultswithin +/– 1 color block.Color Intensity120100806040200Analyte ConcentrationFigure A—A quantitative test showing the direct responsebetween analyte concentration and color intensity.Color Intensity120100806040200Analyte ConcentrationFigure B —A semi-quantitative test showing that thecolor intensity that develops in response to analyteconcentration is not very precise because of the influenceof external factors such as the intrinsic color of the urinesample and sample handling.

MATERIALS AND METHODS: Samples of canine,feline and equine urine (~ 3 mls each) were collectedat three veterinary clinics. A total of 203 samples wereanalyzed (115 canine, 66 feline and 22 equine). Thesesamples were from healthy as well as sick patients.For each sample, 2 IDEXX UA strips were analyzed:one for a visual read and one for an instrument read(UA Analyzer).The samples were also run on the referenceinstrument (Bayer Atlas). To run the Atlas, the sampleswere dispensed into Urin-Tek sample tubes andloaded onto the sample carousel. After the sampleIDs were entered into the instrument, the sample wasautomatically dispensed onto the reagent strips, thestrips were incubated and the results printed.RESULTS: The results from the IDEXX UA Analyzerare semi-quantitative in nature and are therefore givenin result ranges or color blocks. Since these resultranges for each analyte are overlapping (see theexample below), results in the expected concentrationrange and in both neighboring ranges (+/– 1 colorblock) are considered acceptable.Reflectance100%90%80%70%60%50%40%30%20%10%0%neg50 mg/dLGlucose100 mg/dL300 mg/dL1000 mg/dL1 10 100 1000 10000Analyte ConcentrationDISCUSSION: There was a high level of agreementbetween the results from the IDEXX UA Analyzer andthe visually read UA Strips as well as to the referenceinstrument, the Bayer Atlas. In two cases, there weregross disagreements between the IDEXX UA Analyzerand the Bayer Atlas. For bilirubin, the UA Analyzer hada negative result, while the Atlas’s result was “large,”a 3– concentration range difference. When the samplewas sent to a reference lab for analysis, the resultsconfirmed the UA Analyzer’s result. The second casein which there was a disagreement between the twoanalyzers involved Protein. The UA Analyzer had anegative result, while the Atlas had a “>300” result, a4– concentration range difference. Again, the referencelab result confirmed the UA result.Because all the comparative results had a greater than85% agreement, the acceptance criteria have beenmet for the validation of canine, feline and equine urinesamples for IDEXX UA Strips and the IDEXX VetLab ®UA Analyzer against the reference instrument, BayerAtlas.CONCLUSION: The IDEXX UA Analyzer and UAStrips provide accurate and reliable semi-quantitativeurinalysis test results compared to the Bayer Atlasreference method for canine, feline and equinesamples. The IDEXX VetLab UA Analyzer and UAStrips allow practitioners to offer their clients a morecomplete diagnostic profile by running a quick andeasy in-house urinalysis test.The agreement between the IDEXX UA Strips visualresult, the IDEXX VetLab ® UA analyzer result and thereference instrument result are all summarized in thefollowing table:Visual vs.UA AnalyzerVisual vs.AtlasUA Analyzervs. AtlasBilirubin 94% 98% 99%Blood 99% 94% 92%Glucose 99% 97% 98%Ketone 99% 100% 100%Leukocytes 98% 97% 98%Protein 96% 97% 90%Urobilinogen 98% 100% 96%pH 100% 96% 98%One IDEXX DriveWestbrook, Maine 04092 USAidexx.com© 2006 IDEXX Laboratories, Inc. All rights reserved. • 09-65804-00 (9)IDEXX UA and IDEXX VetLab are trademarks or registered trademarksof IDEXX Laboratories, Inc. in the United States and/or other countries.