α2‐Macroglobulin Concentrations in Canine and Equine Serum Donors

Purpose To determine if serum α2‐macroglobulin (A2M) concentration varies based on donor species—canine or equine—and signalment. Methods Serum A2M concentration ([A2M]) was measured in healthy dogs ( n = 30) and horses ( n = 31) using species‐specific ELISAs. Results Canine and equine [A2M] median (IQR; range) were 98.70 ng/mL (92.79 ng/mL; 34.33–696.18 ng/mL) and 557 000 ng/mL (437 900 ng/mL; 62 600–3 042 900 ng/mL), respectively. Equine [A2M] was significantly higher than canine [A2M]. Depending on the statistical analysis performed, sex had either no statistical ( p = 0.17) or medium practical ( η 2 = 0.07) effect on canine serum [A2M], with male dogs having higher [A2M] practically. There was no association between serum [A2M] and duration of serum storage at −80°C. Conclusions Equine serum [A2M] was exponentially higher than that of dogs. Sex may affect [A2M] in dogs. Further study is needed to evaluate how this difference affects antiprotease activity.