Evaluation of Two Commercial ELISA Kits for Measuring Equine Serum Gastrin Compared to Radioimmunoassay

Simple Summary Gastric disease in horses is common and has significant effects on welfare and performance. Gastrin is a hormone involved in the control of gastric acid secretion. Investigations into the effect of gastrin on gastric disease are important for further understanding of the disease and its treatment. However, there has only been one assay validated for the measurement of gastrin in horses. This study aimed to compare the performance of two commercially available, non-validated assays to the previously validated assay. The results showed poor performance of both non-validated assays, and do not support their use for gastrin measurement in future research.Abstract Gastrin is an important hormone involved in gastric acid secretion. Despite its importance, validated methods other than radioimmunoassay (RIA) to assess serum gastrin concentrations in horses are lacking. This study aims to determine the agreement between ELISA and RIA in quantifying equine serum gastrin concentrations. Serum gastrin concentrations were quantified using two ELISA kits and RIA. Samples (196) from 14 horses at different time points were analyzed using one ELISA kit and RIA, selected samples (7) were analyzed using a second ELISA kit, and the correlation between methods was calculated. The level of agreement was analyzed by Bland-Altman analysis and differences between ELISA and RIA were plotted against averages for each sample. The Pearson correlation between gastrin concentrations measured by ELISA and the RIA was 0.27 and -0.32 for ELISA kit 1 and kit 2, respectively. Mean bias (ELISA-RIA) was 198.40 pg/mL (95% CI: -142.95-539.76) and -17.90 pg/mL (95% CI: -89.98-54.19) for ELISA kit 1 and kit 2, respectively. Measurements of horse gastrin by both ELISA methods were highly variable, with an unacceptable correlation to the reference method, RIA. Using non-validated ELISA methods to quantify horse gastrin cannot be recommended.