Analytical and Clinical Evaluation of Two Methods for Measuring Erythrocyte Sedimentation Rate in Eastern Indigo Snakes (Drymarchon couperi).

Erythrocyte sedimentation rate (ESR) is a hematological test that can detect inflammatory activity within the body. Although not specific for any particular disease, ESR is often used as a screening "sickness indicator" due to its reliability and low cost. The Westergren method is a manual ESR technique commonly used but requires special graduated pipettes and over 1mL of whole blood, precluding its use in smaller patients where limited sample volumes can be obtained. A modified micro-ESR technique has been described using hematocrit capillary tubes but is used less commonly. ESR has been reported to be a useful inflammatory indicator in gopher tortoises (Gopherus polyphemus) and box turtles (Terrapene spp.) but not in Florida cottonmouth snakes (Agkistrodon conanti). Having an inexpensive screening test for inflammation can help guide medical decisions within conservation efforts of imperiled species. This study evaluated the correlation between these two ESR methodologies in threatened eastern indigo snakes (Drymarchon couperi, EIS) and found a very strong correlation (rs = 0.897), without constant or proportional biases and a reference interval of 0 (90% CI -1-1)-9 mm/h (90% CI 8-11) was defined. Additionally, a significant difference was found between healthy EIS and EIS in mid-ecdysis (p = 0.006) and EIS with gastric cryptosporidiosis (p = 0.006), indicating ESR as a useful inflammatory indicator in EIS.