Study validates stall-side IgG assay for neonatal foals
Bottom line
A new Equine Veterinary Journal study validated a stall-side immunoglobulin G assay, Sidekick, for use in foal care, finding that the lateral-flow test and handheld reader produced rapid, repeatable IgG measurements with strong agreement to established laboratory methods. The study evaluated the assay against radial immunodiffusion, the traditional reference method, and an immunoturbidimetric assay, and concluded it could reliably identify foals with failure of passive transfer, particularly at the clinically important threshold below 4 g/L. The device delivers quantitative results in about five minutes, which is the practical change here: clinicians may be able to make treatment decisions without waiting on lab turnaround. (beva.onlinelibrary.wiley.com)
Why it matters: Failure of passive transfer remains a major driver of illness and death in neonatal foals because they depend on colostral IgG for early immune protection. For equine veterinarians, a validated point-of-care assay could tighten the window between testing and intervention, especially in ambulatory and breeding-farm settings where access to rapid laboratory testing is limited. Existing guidance and recent coverage both underscore that timely IgG assessment is central to deciding whether to supplement colostrum, administer plasma, or continue monitoring. (pubmed.ncbi.nlm.nih.gov)
What to watch: Watch for broader field adoption, independent validation in larger practice settings, and whether clinics begin integrating quantitative stall-side IgG testing into standard foal screening protocols. (sidekickanimalhealth.com)
Key facts
- Test name
- Sidekick
- Use
- Stall-side immunoglobulin G assay for neonatal foals
- Clinical purpose
- Diagnose failure of passive transfer
- Reference methods
- Radial immunodiffusion and immunoturbidimetric assay
- Key threshold
- Below 4 g/L
- Result time
- About five minutes
- Performance
- Strong agreement with established laboratory methods
- Repeatability
- Mean coefficient of variation of 6.9%
- Linearity and recovery
- 94% to 110% between 2 and 20 g/L
A newly published Equine Veterinary Journal paper adds peer-reviewed validation to a stall-side IgG test designed for neonatal foals, giving equine practitioners new evidence that rapid, quantitative immunoglobulin testing can be done reliably in the barn. The assay, Sidekick, combines a lateral-flow cartridge with a handheld reader and was studied as a point-of-care tool for diagnosing failure of passive transfer, a condition that leaves foals vulnerable to early infection and sepsis. (pubmed.ncbi.nlm.nih.gov)
That matters because passive transfer is a narrow-window problem. Foals are born dependent on colostrum for immunoglobulin uptake, and inadequate transfer is strongly associated with morbidity and mortality. Traditional quantitative testing methods such as radial immunodiffusion are well established, but they require laboratory processing and can delay treatment decisions. Over time, clinicians have relied on a mix of lab assays and faster screening tools, including immunocrit and semiquantitative stall-side tests, each with tradeoffs in speed, precision, and accessibility. (pubmed.ncbi.nlm.nih.gov)
In the new validation study, investigators assessed the Sidekick assay’s analytical and clinical performance using diluted foal serum samples across a clinically relevant range, then compared results with radial immunodiffusion and immunoturbidimetric testing. According to the abstract and Wiley summary, the assay showed strong linearity across the measurable range, with recoveries from 94% to 110% between 2 and 20 g/L, and a mean coefficient of variation of 6.9%, supporting repeatability. The authors concluded the test could be implemented effectively to identify failure of passive transfer below 4 g/L, while noting the expected tradeoff that lateral-flow systems are less sensitive at higher IgG concentrations than laboratory methods. (beva.onlinelibrary.wiley.com)
The commercial product positioning matches that clinical use case. Sidekick Animal Health says its IgG assay provides quantitative results from 80 to 2000 mg/dL in five minutes and is intended for screening foals at elevated risk of failure of passive transfer. The company has also been building out the broader equine reproductive management platform around the same reader, including a progesterone assay evaluated separately in the literature, suggesting a strategy centered on portable equine diagnostics rather than a single-test launch. (sidekickanimalhealth.com)
Industry reaction so far appears cautiously positive, especially from ambulatory and breeding-focused users. The Horse recently highlighted the ongoing need for faster IgG testing outside referral settings, noting that the gold-standard single radial immunodiffusion test is not practical for many field veterinarians because of turnaround time. On Sidekick’s testimonials page, users from ambulatory and reproductive practices describe the IgG test as a way to avoid choosing between speed and exact values, though those comments should be read as commercial testimonials rather than independent evidence. (thehorse.com)
Why it matters: For veterinary professionals, the significance is less about a brand-new biologic insight and more about workflow. If a stall-side assay can accurately sort foals into complete failure, partial failure, or adequate passive transfer while the veterinarian is still on farm, it can compress the decision timeline for colostrum supplementation, plasma administration, repeat testing, and referral. That is especially relevant because current practice frameworks still emphasize checking foal IgG early, and recent AAEP foaling materials continue to use the familiar cut points of under 400 mg/dL for failure and 400 to 800 mg/dL for partial failure. A quantitative test that fits that decision tree may be particularly useful in ambulatory equine practice. (aaep.org)
There are still limits to keep in view. The published summary indicates the assay performs best around the clinically critical lower thresholds, and the authors acknowledge some loss of sensitivity at higher IgG concentrations compared with lab-based methods. That means the test’s value may be greatest as a rapid triage and treatment tool, rather than a full replacement for every laboratory context. Independent post-publication studies, cost comparisons, and real-world outcome data will help determine how widely it changes standard neonatal foal protocols. (beva.onlinelibrary.wiley.com)
What to watch: The next step is whether additional independent studies, practice-level adoption, and guideline discussions move quantitative stall-side IgG testing from promising option to routine standard of care in foal management. (sidekickanimalhealth.com)