Storage-related artefacts in equine blood result in a pseudo-inflammatory leukogram.
Authors: Parsley Ashley L, Hollingshead Nicholas A, Gruber Erika J
Journal: Equine veterinary journal
Summary
# Editorial Summary Veterinarians working in ambulatory equine practice face a practical dilemma: EDTA blood samples cannot always be analysed immediately or kept refrigerated, yet the effects of delayed analysis on equine haematology results remain poorly characterised. Parsley and colleagues examined how storage temperature and duration affect leukocyte counts and morphology by storing blood from 13 clinically healthy horses at four conditions (4°C, 3–19°C, 22°C, and 37°C) and performing automated differential counts and blood smear evaluation over 120 hours. Whilst automated WBC counts remained relatively stable for 24 hours across refrigerated, cooler, and room-temperature samples, significant decreases occurred after 48 hours in cooler-stored and room-temperature samples; at body temperature (37°C), changes were even more dramatic, with pyknotic cells increasing by 4 hours and WBC concentration falling by 8 hours. Importantly, storage-dependent artefacts—including cell swelling, rupture, hypolobulation, and cytoplasmic vacuolation—developed progressively at all temperatures and created a pseudo-inflammatory appearance that could mislead clinical interpretation and influence management decisions. For practitioners unable to refrigerate samples immediately, results should be interpreted cautiously if analysis is delayed beyond 24 hours, and where possible, samples kept at refrigeration temperature to extend the reliable window for interpretation to approximately 48 hours.
Read the full abstract on PubMed
Practical Takeaways
- •For ambulatory practice: refrigerate blood samples immediately and process within 24 hours to avoid misleading leukocyte counts and differential results that could prompt unnecessary treatment
- •Samples stored at room temperature or in coolers with ice packs for longer than 48 hours show significant artefactual changes; plan to deliver samples to the laboratory within this timeframe when possible
- •Be cautious interpreting neutrophil abnormalities from delayed samples—apparent left shifts or low counts may be storage artefacts rather than true inflammatory responses, especially if clinical signs don't match lab findings
Key Findings
- •Automated leukocyte counts remained stable up to 24 hours at refrigeration (4°C), cooler (3-19°C), and room temperature (22°C), but decreased significantly after 48 hours at cooler and room temperature conditions
- •Storage at 37°C resulted in increased pyknotic cells by 4 hours and decreased WBC concentration by 8 hours
- •Storage-dependent morphological changes including cell swelling, ruptured cells, hypolobulated neutrophils, and cytoplasmic vacuolation occurred at all temperatures but appeared later under refrigeration
- •Pseudo-inflammatory leukogram patterns could occur within 24 hours in some samples, potentially leading to misinterpretation of results and altered patient management