Evaluation of the Sidekick point-of-care progesterone lateral-flow assay for use in equine reproductive management.

Abstract

A point-of-care (POC; stall-side) test for progesterone that delivers rapid, accurate results has the potential to transform equine reproductive care. We evaluated the analytical and clinical performance of a POC device (Sidekick) that incorporates a progesterone lateral-flow assay (LFA) with a reader, and compared it with established methods (radioimmunoassay [RIA] and chemiluminescence immunoassay [CLIA]). Analytical performance was assessed using serially diluted mare plasma (0-8 ng/mL progesterone) to estimate precision and percent recovery. Clinical accuracy was assessed by comparison with RIA and CLIA on 19 paired serum samples. Agreement was evaluated by regression analyses and ordinal concordance across clinically relevant progesterone bands. The LFA had excellent recovery (90-102%) across 4-8 ng/mL, strong repeatability (CV 4-15%), and high reproducibility between 2 laboratories (CV 9.9%). Ordinal agreement with reference standards was near-perfect in spiked samples (κ = 0.94) and substantial in clinical samples versus both RIA (κ = 0.77) and CLIA (κ = 0.79). Cross-reactivity with the synthetic progestin, altrenogest, was tested at pharmacologic concentrations; no cross-reactivity was detected. Limitations of our study include an observed bias, potentially caused by the matrix differing between methods (serum vs. plasma). Additionally, a narrow validated range could cause underestimation of high concentrations. The LFA in the Sidekick device provided rapid, accurate, and clinically meaningful progesterone results in mares across 4-8 ng/mL, which would enable on-the-spot decisions and avoid delays from sample processing, transport, and result reporting.