Validation of a stall-side immunoglobulin assay for use in equine reproductive management.

Overview

• This study evaluated a new stall-side immunoglobulin G (IgG) test, called Sidekick, designed for rapid, point-of-care measurement of IgG levels in foals to assess passive transfer from the mare.
• The goal was to determine if this test provides accurate and repeatable results comparable to gold-standard laboratory methods, enabling faster clinical decisions for foal care.

Background

• Equine foals rely on immunoglobulin G (IgG) obtained through their mother’s colostrum shortly after birth, a process called passive transfer.
• If this transfer fails (referred to as Failure of Passive Transfer, FPT), foals have a high risk of infections and sepsis due to lack of adequate immunity.
• Current diagnostic methods—Radial Immunodiffusion (RID) and immunoturbidimetric assays—are accurate but require laboratory processing, leading to delays in obtaining results.
• Rapid, reliable stall-side testing could significantly improve clinical management, allowing veterinarians to quickly identify foals with FPT and initiate timely treatment.

Objective

• To assess the analytical performance (accuracy, repeatability) and clinical utility of the Sidekick stall-side IgG lateral-flow test (LFD) as a point-of-care diagnostic tool.
• To compare Sidekick test results with established laboratory assays (RID and immunoturbidimetric assay) for IgG quantification.
• To evaluate agreement in IgG levels measured from whole blood versus plasma samples using the Sidekick device.

Methods

• Study design: Retrospective cohort analysis using samples from 10 foals.
• Sample cohorts: Divided into two groups, one with successful passive transfer (adequate IgG levels) and the other with FPT (low IgG levels).
• Testing procedures:
  • Sidekick LFD test used on serially diluted foal serum/plasma samples ranging from 0.8 to 20 g/L IgG (three replicates per dilution) to assess accuracy and repeatability.
  • Sidekick results compared with results from RID and immunoturbidimetric assays (gold standards).
  • Comparison of IgG quantification from matched whole blood and plasma samples in three foals to determine sample type impact on results.

Results

• The Sidekick stall-side LFD test demonstrated:
  • Excellent recovery rates, between 96.3% and 109.5% within the critical clinical IgG range of 4-8 g/L.
  • High repeatability with coefficient of variation (CV%) values between 3.7% and 10%, indicating consistent results across replicates.
  • Strong agreement with the reference laboratory assays (RID and immunoturbidimetric), confirming accuracy.
  • Strong correlation between blood and plasma sample results measured by the Sidekick device, indicating versatility of sample type for testing.
• Study was limited by a small sample size (10 foals), indicating a need for further validation on larger cohorts.

Conclusions

• The Sidekick stall-side immunoglobulin assay provides reliable, repeatable IgG quantification at the point-of-care.
• This capability allows veterinarians to make rapid, informed decisions regarding treatment of foals with suspected failure of passive transfer.
• Use of the Sidekick device reduces delays associated with laboratory sample processing, transport, and result turnaround times.
• Overall, the test shows promise for improving clinical management and survival outcomes in equine neonates by facilitating timely intervention.
• Future research with larger foal populations is warranted to further confirm clinical utility and establish robust operational guidelines.