Effects of sample storage time and temperature on equine complete blood counts

Background Equine blood samples are often collected in uncontrolled, distant environments and stored for later analysis. Aims This study aimed to determine how sample storage methods influence complete blood count (CBC) parameters, hypothesizing that temperature and time elapsed from collection to analysis would affect CBC parameters. Methods Blood samples were collected from 10 healthy Quarter Horse mares (age: 13 ± 4.5 years old) and stored in EDTA tubes at room temperature (22°C), above ice (8°C), refrigerated (4°C), or in contact with ice (2°C). The IDEXX ProcyteDx was used to obtain CBCs at 3, 6, 12, 24, 48, and 72 hours after collection. Data were analyzed using the Kruskal-Wallis test with Dunn’s post hoc analysis and Benjamini-Hochberg correction. Significance was set to P ≤ 0.05. Results A reduction of monocytes and elevation of basophils was seen as early as 48 hours at 2°C, 4°C, and 8°C and occurred to a greater extent at 22°C, likely due to a greater degree of cellular degradation. Changes to red blood cell parameters occurred as early as 48 hours after collection at 4°C and 8°C and were more exaggerated at 22°C. Storage at 2°C resulted in earlier differences in red blood cell parameters. In contrast with previous studies, platelet counts were increased with time in all cooled storage methods, exhibiting a progressive temperature-dependent response as early as 24 hours. Conclusion It appears equine blood samples are most stable when stored at 4°C or 8°C and run within 48 hours when using the IDEXX Procyte Dx.