Agreement between Total Leukocyte Count Methodologies in Free-Ranging South American Sea Lions (Otaria byronia) and Peruvian Fur Seals (Arctocephalus australis)
Abstract
South American sea lions (Otaria byronia) and Peruvian fur seals (Arctocephalus australis ssp.) are locally endangered species in Peru. As sentinels of ecosystem health, monitoring trends in these populations is critical.1 A key component of health assessments is bloodwork monitoring.2-5 Several methodologies determine total leukocyte count, including blood film estimates, manual cell counts, and point-of-care analyzers, yet no studies have evaluated agreement between methods in pinnipeds. The purpose of this study was to assess agreement between total leukocyte counts determined by blood film estimate, Leuko-TIC®a, HemoCue®b, and UNOPETTE®c methods using archival samples from pinnipeds at Punta San Juan, Peru. Blood film estimates were prospectively performed to ensure uniformity. Data was then compared to retrospective leukocyte counts obtained from both species between 2009–2019 using the other methodologies. Agreement in hematologic counts between the different methods was evaluated using Passing-Bablok regression (PB) and Bland-Altman plots (BA). A total of 295 individuals (201 Arctocephalus, 94 Otaria) were included in the analysis. Data represented 205 adults and 90 juveniles and was comprised of 127 males and 168 females. The blood film estimate method resulted in the highest WBC values (p<0.0001) and Leuko-TIC® counts were significantly higher than HemoCue® counts (p<0.0001). Constant and proportional error was present between the blood film estimate method and each of the other methods based on PB, while there was complete agreement between Leuko-TIC® and HemoCue® methods in both PB and BA plots.
This study’s results contribute to the overall knowledge of evaluating health in free-ranging pinniped populations.
Acknowledgements
The authors thank Marco Cardeña and all the biologists who have supported research sample and data collection. We further thank Dr. Gwen Jankowski, Dr. Jenny Meegan, and the veterinary teams who have assisted with anesthesia and sample collection. Funding for components of this research has been provided by generous support from the Chicago Board of Trade Endangered Species Fund, Paul M. Angell Family Foundation, and the Feay Family. We acknowledge the Peruvian government agencies SERNANP, for access inside the RNSIIPG-Punta San Juan reserve, and AGRORURAL for use of field facilities. Research and samples were collected under permits RJ No. 09-2010-, 23-2011-, 022-2012-, 09-2013-, 024-2014, 008-2015-, 019-2016-SERNANP-RNSIIPG. The authors also thank VCA Animal Hospitals and Antech Diagnostics for contributions to this study.
Endnotes
a. BioAnalytic GmbH, 79224 Umkirch, Germany
b. HemoCue America, Brea, California 92821, USA
c. BD Company, Franklin Lakes, New Jersey 07417, USA
*Presenting author
+Student presenter
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