Wellness Ready Insulin Test Performance and Validation
Wellness Ready Test Dynamic Range (20.0 to 99.9 uU/mL)
The dynamic range of the Wellness Ready Insulin Test is 20.0 to 99.9 microunits of insulin per milliliter (µU/mL). Sample insulin concentrations within this dynamic range will be displayed in microunits of insulin per milliliter on the digital reader. If the sample insulin concentration is below the minimum of the dynamic range of the assay, < 20.0 will be displayed by the test reader. If the sample insulin concentration is above the maximum of the dynamic range, > 99.9 will be displayed.
Download the UC-Davis validation study article [Journal of Veterinary Diagnostic Investigation]
Methodology
The University of California, Davis, School of Veterinary Medicine and Center for Equine Health performed Wellness Ready Insulin Tests (in duplicate) on 99 equine whole blood samples obtained from 51 horses and shipped 99 corresponding plasma samples to Cornell University College of Veterinary Medicine Animal Health Diagnostic Center for insulin determination (in duplicate) via radioimmunoassay (RIA). Each replicate of the Wellness Ready Insulin Test was treated as a separate test result (198 total), whereas the average of the two Cornell RIA replicates was used to value assign a given sample. The sensitivity, specificity and overall accuracy of the Wellness Ready Insulin Test when a single insulin concentration cutoff at 45, 50, or 65 µU/mL is applied to both the Wellness Insulin Test results and the Cornell RIA values are summarized in the table below.
Wellness Ready Assay Sensitivity, Specificity and Overall Accuracy
| Insulin Cutoff [Cornell RIA] |
WR Sensitivity | WR Specificity | Overall Accuracy | ||||||||||||
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©Berryhill EH, Urbina N, Herberg de Alonso F
Interpretation of Test Performance
From the table above, at a single insulin concentration cutoff of 45 µU/mL, the sensitivity of the Wellness Ready Insulin Test is 87%. This means that the Wellness Ready Insulin Test measured > 45 µU/mL in 87% of the samples where the corresponding Cornell RIA values were also > 45 µU/mL. Similarly, at single insulin concentration cutoffs of 50 and 65 µU/mL, the sensitivities of the Wellness Ready Insulin Test are 88% and 91%, respectively. This means that the Wellness Ready Insulin Test measured > 50 and 65 µU/mL in 88% and 91% of the samples where the corresponding Cornell RIA values were also > 50 and 65 µU/mL.
The table above also shows a specificity of 92% for the Wellness Ready Insulin Test at a single insulin concentration cutoff of 45 µU/mL. This means that the Wellness Ready Insulin Test measured ≤ 45 µU/mL in 92% of the samples where the corresponding Cornell RIA values were also ≤ 45 µU/mL. Similarly, at single insulin concentration cutoffs of 50 and 65 µU/mL, the specificities are 92% and 96%, respectively. This means that the Wellness Ready Insulin Test measured ≤ 50 and 65 µU/mL in 92% and 96% of the samples where the Cornell RIA values were also ≤ 50 and 65 µU/mL.
At a single insulin concentration cutoff of 45 µU/mL, the overall accuracy of the Wellness Ready Insulin test is 90%. This means that the Wellness Ready Insulin Test measured either ≤ 45 µU/mL or > 45 µU/mL in 90% of the samples where the corresponding Cornell RIA values were also either ≤ 45 µU/mL or > 45 µU/mL. Similarly, at single insulin concentrations cutoffs of 50 and 65 µU/mL, the overall accuracies are 90% and 95%, respectively. This means that the Wellness Ready Insulin Test measured either ≤ 50 and 65 µU/mL or > 50 and 65 µU/mL in 90% and 95% of the samples where the corresponding Cornell RIA values were also either ≤ 50 and 65 µU/mL or > 50 and 65 µU/mL.
Understanding Insulin Concentration Cutoffs
The cutoff values used in the Wellness Ready Insulin Test validation studies are commonly used insulin concentration reference points for identifying horses with appropriate insulin regulation (insulin concentrations less than cutoff) and horses with insulin dysregulation (insulin concentrations greater than cutoff) when horses are tested in a non-fasted state (50 uU/mL cutoff) or when horses undergo dynamic testing with a low-dose oral sugar test (45uU/mL cutoff) or high-dose oral sugar test (60 uU/mL), respectively (Equine Endocrinology Group 2020).
Wellness Ready does not intend to instruct veterinarians on how to conduct insulin testing in horses (fasted versus non-fasted; unchallenged versus dynamic testing) or to specify which insulin concentration cutoffs to use to identify horses with normal insulin regulation or insulin dysregulation. Wellness Ready developed its stall side insulin test as a tool that veterinarians can use to conveniently and rapidly determine the blood insulin concentration of a horse. Wellness Ready expects that veterinarians will consult with their colleagues and key opinion leaders to determine the insulin testing protocol and insulin test cutoff values that they will use in assessing the metabolic status of their equine patients.