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

Overview

• This study investigated how the storage time and temperature of equine blood samples affect the accuracy of complete blood count (CBC) results.
• The researchers found that storage conditions notably influence blood cell counts, and optimal stability is achieved when samples are stored at 4°C or 8°C and analyzed within 48 hours.

Background and Purpose

• Equine blood samples are frequently collected in field conditions where immediate analysis is not feasible.
• Samples must often be stored and transported before laboratory testing.
• The study’s objective was to identify how different storage temperatures and times between collection and analysis affect the CBC parameters in horse blood.
• The hypothesis was that both temperature and duration until analysis would significantly impact CBC results.

Methods

• Blood was collected from 10 healthy Quarter Horse mares, averaging 13 years old.
• Samples were placed in EDTA tubes to prevent clotting and stored at four different temperature conditions:
  • Room temperature (22°C)
  • Above ice (8°C)
  • Refrigerated (4°C)
  • In contact with ice (2°C)
• CBC measurements were performed using the IDEXX Procyte Dx analyzer at multiple time points:
  • 3 hours, 6 hours, 12 hours, 24 hours, 48 hours, and 72 hours post-collection
• Statistical analyses involved non-parametric tests (Kruskal-Wallis) with multiple comparisons adjustments to identify significant changes over time and temperature.
• Significance threshold was set at p ≤ 0.05.

Key Findings

• Monocytes showed a reduction starting at 48 hours when stored at cooler temperatures (2°C, 4°C, 8°C) with a greater reduction at room temperature, likely due to increased cellular degradation at higher temperature.
• Basophil counts increased from 48 hours at all tested temperatures, again more pronounced at 22°C.
• Parameters related to red blood cells began to show changes starting at 48 hours at 4°C and 8°C, with these changes being even more substantial at 22°C.
• Unexpectedly, platelet counts increased over time during all cooled storage conditions, starting as early as 24 hours:
  • This increase exhibited a temperature-dependent pattern, with cooler temperatures correlating with greater platelet count changes.
  • This finding contrasts with previous research that suggested platelet counts would decrease or remain stable over time.
• Storage at the coldest temperature (2°C) led to earlier and more pronounced alterations in red blood cell parameters compared to the other cooling temperatures.

Conclusions and Practical Implications

• Equine blood stability for CBC analysis varies significantly with storage temperature and time.
• Samples stored at moderate refrigeration temperatures (4°C or 8°C) demonstrated greater stability up to 48 hours.
• Storage at room temperature or at ice contact temperature (2°C) led to more rapid and pronounced changes in several blood cell parameters.
• Given these findings, for accurate CBC analysis using the IDEXX Procyte Dx:
  • Store equine blood samples at 4°C or 8°C whenever possible.
  • Perform CBC within 48 hours of collection to minimize sample degradation and inaccurate results.
• The increase in platelet counts with cooled storage highlights the importance of considering storage conditions when interpreting CBC results from equine blood samples.

Study Limitations and Future Directions

• The sample size was limited to 10 horses, which, while sufficient for detecting trends, may limit generalizability.
• Only healthy adult mares of one breed were tested; other breeds, ages, or health conditions may impact results.
• Further research could explore mechanisms behind the unexpected platelet count increase during cooled storage.
• Additional studies might evaluate other storage media or preservatives to improve sample stability.
• Validation with other CBC analyzers could help confirm if these findings are consistent across different technologies.