Delays in processing equine blood tests can affect results
Delays in processing equine blood tests can affect results Laboratory tests are often used to reach a diagnosis. Samples should be analysed as soon as possible after being taken so that the results accurately represent the animal's condition. Now this is fine in a hospital situation, where the samples can be analysed immediately. But many veterinarians submit samples to specialist laboratories, rather than performing the analysis themselves. Does the delay in analysing the samples significantly affect their accuracy? Mr David Rendle and his colleagues conducted a study to investigate at Liphook Equine Hospital. They collected blood samples from horses admitted to the hospital and analysed them immediately (within 3 hours). The samples were then stored at room temperature (20 - 25°C) and the analyses were repeated 24, 48 and 72 hours later. |  |
The greatest effect was seen in substances used as markers of tissue damage that are also present within the red blood cells. Damage to the red cells (haemolysis) releases them into the serum.
The concentration of AST, (aspartate aminotransferase) LDH (lactate dehydrogenase) CK (creatine kinase) and magnesium increased significantly over time in the stored whole blood samples. Taken at face value, such changes would suggest a diagnosis of muscle damage - when in fact they may be just due to deterioration in the sample.
The total Bile Acids also increased.
On the other hand GLDH (glutamate dehydrogenase), an enzyme that indicates damage to liver cells, fell when the analysis was delayed. After 72 hours the difference became statistically significant.
Glucose levels in the stored samples (both whole blood and separated serum) fell. This still occurred, but to a lesser extent, when the sample was preserved with fluoride-oxalate to inhibit glucose metabolism.
Is there any benefit in separating the serum from the clot before storing or mailing the sample? The researchers found that doing so did give more accurate results. However, the improvement in accuracy was not statistically significant. Changes that might affect clinical interpretation still occurred. So separating the serum from the clot seems to be of limited value if analysis is to be delayed by 2-3 days.
It is important to bear these effects in mind when interpreting the results of blood tests if the analysis has been delayed.
The work has been reported in the Equine Veterinary Journal. The authors suggest that the findings could be used to help interpret results when a delay in analysis may have resulted in changes in the blood sample.
For more details see:
Stability of common biochemistry analytes in equine blood stored at room temperature.DI Rendle J Heller, KJ Hughes, GT Innocent, AE Durham.
Equine Vet J (2009) 41, 428 - 432.
Reproduced with kind permission of Mark Andrews BVM&S CertEP MRCVS
© Copyright Mark Andrews - Equine Science Update 2009
Added on: 19/09/09.
Email this article to a friend or shareVoices for Horses offers news, articles and videos from third party providers unless otherwise stated. We do not endorse the views expressed or content and make it available to you only as a service. All news items, articles and videos are copyright of the authors, film makers and original publications.
