Comparison of the VITROS 250 and the IDEXX VetTest Chemistry
Analyzer for Urine Protein:Creatinine Ratios in Dogs and Cats.
The importance of rapid laboratory results has been well-established in veterinary medicine. An in-clinic diagnostic test gives
the practitioner the ability to make an immediate diagnosis and
provide timely treatment. The new IDEXX Urine P:C Ratio is an
in-house, fully quantitative assessment of urinary protein loss. The
objective of this study was to compare the UPC results between a
reference instrument (VITROS® 250) and the new IDEXX Urine P:C Ratio
for the VetTest® Chemistry Analyzer.
Paired feline and canine urine samples were collected from 150
patients (100 canine samples, 50 feline samples). Testing was
performed on each analyzer within two hours of one another and
according to manufacturer’s instructions with appropriate dilutions.
Each analyzer was maintained to manufacturer's specifications,
including handling of the test materials and performance of quality-control procedures.
The linear regression scatterplot for the paired UPC ratios shows
a high level of association between the two instruments (R2=0.97).
The Urine P:C Ratio is comprised of two components, a urine protein
test and a urine creatinine test. Each test was independently analyzed
to ensure that component results were comparable between the
instruments. The linear regression scatterplot for the paired urine
protein tests shows a high level of agreement between the instruments
(R2=0.97). Samples above the dynamic range were diluted according to
manufacturer’s instructions with dynamic range maximums of 200 mg/dL
for the VITROS 250 analyzer and 400 mg/dl for the IDEXX VetTest analyzer. The linear regression
scatterplot for the paired urine creatinine tests also shows a high
level of association between the two instruments (R2=0.96). As per
manufacturer instructions, all urine samples were diluted 1:21, with
samples greater than 350 mg/dL requiring a second dilution of 1:2.
There was strong association between the VITROS 250 and the IDEXX
VetTest analyzers when comparing UPC results. Moreover, the individual
analytes for urine protein and urine creatinine also showed a high
level of association. This result correlates well with the fact that
both the Vitros 250 and the IDEXX VetTest analyzers use dry-slide technology.
The urine protein slide (UPRO) uses a dye-binding assay and has
dynamic ranges of 5 to 200 mg/dL (Vitros 250) and 5 to 400 mg/dL
(IDEXX VetTest). The urine creatinine slide uses an enzymatic assay
and has a dynamic range of 1.05 to 346.5 mg/dL (Vitros 250) and 5 to
350 mg/dL (IDEXX VetTest). The UPC ratios and both urine protein and
urine creatinine results compare favorably between the Vitros 250 and
the IDEXX VetTest analyzers.
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