Pre-analytical stability of sorbitol dehydrogenase in equine heparinized plasma.
Authors: Fouché N, Oesch S, Gerber V, Richter H, Howard J, Peters L M
Journal: Veterinary journal (London, England : 1997)
Summary
Sorbitol dehydrogenase (SDH) is acknowledged as the most sensitive and specific marker of hepatocellular damage in horses, yet its notorious instability in stored samples has severely limited its clinical utility; this study investigated how SDH activity behaves when equine heparinized plasma is held at different temperatures for extended periods to determine whether more widespread laboratory use might become feasible. Researchers collected blood samples from twenty clinical horses, immediately centrifuged them into lithium-heparin tubes, and measured baseline SDH activity within one hour of collection, then re-measured the same aliquots after storage at room temperature, 4°C, and −20°C at 4, 24, and 72 hours post-collection. The key finding was that SDH remained acceptably stable (within ±20% of baseline) for four hours across all temperature conditions and for 24 hours specifically when refrigerated at 4°C, though statistically significant degradation occurred in room-temperature and frozen samples beyond these timeframes. For practitioners, these results suggest that submitting heparinized plasma samples refrigerated overnight is now defensible practice for SDH analysis, potentially enabling more horses with suspected liver disease to benefit from this highly specific diagnostic marker rather than relying on less precise hepatic enzymes like GGT and ALP. The practical implication is particularly valuable for rural practices and those distant from laboratory facilities, where room-temperature transport has previously rendered SDH results unreliable.
Read the full abstract on PubMed
Practical Takeaways
- •If you need to submit plasma for SDH analysis, keep samples refrigerated at 4°C rather than frozen or at room temperature for optimal results
- •SDH samples are reliable for up to 4 hours at any temperature, but for longer delays before analysis, refrigeration at 4°C is essential to prevent false low results
- •This improved understanding of SDH stability makes it more practical to use as a sensitive hepatic injury marker in clinical practice rather than being limited to reference labs with rapid turnaround
Key Findings
- •SDH activity remained stable (within ±20%) for 4 hours at all storage temperatures (room temperature, 4°C, -20°C)
- •SDH activity remained stable at 4°C for 24 hours but showed significant degradation at room temperature and -20°C after 24 hours
- •Storage at 4°C produced lower mean absolute percentage error and narrower limits of agreement compared to room temperature or -20°C storage
- •Knowledge of SDH pre-analytical stability may enable broader clinical use of this sensitive hepatocellular injury marker in equine practice