Small Animal Internal Medicine

Research Abstract

GI19 - Linearity, Precision, and Reproducibility of the VetScan cPL Rapid Test

Thursday, June 14
4:45 PM - 5:00 PM
Location: WSCC 618/619

Measurement of serum concentrations of pancreatic lipase immunoreactivity (PLI) has become the standard for the diagnosis of pancreatitis in both dogs and cats. Recently, a new patient-side test for measurement of canine PLI (cPLI), the VetScan cPL rapid test for use with the VetScan VUE analyzer, has become available. Marketing material as well as the analyzer read-out suggest that this new assay provides accurate serum cPLI concentrations within a margin of ±65 µg/L compared to the Spec cPL® assay, but analytical or clinical validation data for this assay have not been published. The goal of this study was to evaluate linearity, precision, and reproducibility of the VetScan cPL rapid test.


Leftover serum samples from clinical submissions to the Gastrointestinal Laboratory at Texas A&M University were used for this study. For assessment of linearity, 7 good quality (i.e., not lipemic, hemolyzed, or icteric) serum samples throughout the working range of the cPLI assay as measured by Spec cPL® (Idexx Laboratories, Portland, Maine) were analyzed using the VetScan cPL rapid test assay (Abaxis, Union City, CA) undiluted and diluted at 1:2, 1:4, and 1:8, and observed/expected ratios were calculated. Intra-assay variability was assessed with 3 good quality serum samples analyzed 10 times on 4 different VUE analyzers at the same time. For assessment of inter-assay variability, 10 good quality serum samples were analyzed on 8 different days on the same machine (7 samples were analyzed on a single machine, while 2 samples were analyzed on 4 machines each).


Observed to expected ratios for dilutional parallelism ranged from 77.4 to 162.9%, with a mean of 119.3%. Intra-assay variability ranged from 16.9 to 36.7% (mean %CV for all samples and machines: 25.1%). Inter-assay variability ranged from 14.1% to 51.2% (mean %CV for all samples and machines: 31.8%) and most samples resulted in two (7 samples) or even three (5 samples) diagnostic bins (i.e., within the reference interval; gray range; suggestive of pancreatitis) during the experiment.


The new VetScan cPL rapid test for the VetScan VUE shows poor linearity. This is of clinical significance as the working range of this assay is very narrow, making dilution necessary for samples with higher cPLI concentrations. Also, the assay is not very precise (mean %CV: 25.1%). Finally, inter-assay variability is unacceptably high (mean %CV: 31.8%), affecting the actual diagnostic bin in many cases. In conclusion, the VetScan cPL rapid test for the VetScan VUE lacked linearity, precision, and reproducibility.

Joerg M. Steiner, MedVet., DrMedVet., PhD, DACVIM, DECVIM-CA, AGAF

Director
Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX

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GI19 - Linearity, Precision, and Reproducibility of the VetScan cPL Rapid Test

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