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Veterinary Normal Ranges

From Joanna Carroll:

What recommendations would you make for veterinary medicine? I work at the North Carolina State University College of Veterinary Medicine Veterinary Teaching Hospital. We just purchased a new automated coag analyzer, the Stago STA Satellite. Currently we have the semi-automated STart 4 by Stago. We have not been using Stago reagents, but we will probably switch to their prothrombin time (PT) reagent and use their calcium chloride for partial thromboplastin time (PTT). If our comparisons are close, can we adjust our current ranges or should we reestablish new?

It is not feasible to acquire normal samples from 60 dogs, cats, and horses in a week, as we have to ask people to bring their pets in, or draw blood at home and bring it in. It is also very difficult to get enough blood to have 5-10 aliquots from each sample. We can manage to get around 30 samples from dogs, sometimes 20 or so from horses. We do want to follow protocol as much as possible, as we pride ourselves in accurate results.

Thank you for your time.
Joanna Carroll MT (ASCP)
Clinical Pathology Lab
NCSU College of Veterinary Medicine

Hello, Joanna, and thank you for your question. Where normal ranges exist, you can legitimately use a confirmatory approach, which typically specifies 20 aliquots from normal subjects. Assay the specimens, compute mean and 95% confidence interval or ±2 SD, compare to the existing normal range, and adjust if necessary. Only if the new normals differ significantly, for instance by >20%, would you want to establish a new normal range from scratch.

In instances where normal aliquots are difficult to collect, for instance, when establishing pediatric values in human medicine, published reference intervals are a reasonable substitute, though slightly less accurate. The key is to establish at what point does an abnormal value trigger intervention.

This is the first question we’ve had on the topic of hemostasis in veterinary medicine, and I would be interested to learn how other veterinary labs establish normals, and also to learn are the most common applications for PTs, PTTs, and other hemostasis tests.

Comments (3)
Apr 13, 2011 8:01am

One of the issues in veterinary medicine is the breed of the
One of the issues in veterinary medicine is the breed of the animal. For example Beagles may have slightly different results compare to Spaniels. In humans the age is of equivalent importance. The Start4 is used in a French veterinary schools to manage PTs under 10 seconds and PTTs under 30. These numbers are not seen in human patients.

Apr 5, 2011 11:54am

Thanks for your comments. Typically we try for 30 normal sa
Thanks for your comments. Typically we try for 30 normal samples from each species that we deal with (dogs, cats, horses). Getting 30 normal dogs is fairly easy, cats and horses however not so easy. We do the best we can and our ranges seem comparable with other veterinary teaching hospitals.

Apr 4, 2011 11:45am

I would suggest to purchase Schalm’s Veterinary Hematology f
I would suggest to purchase Schalm’s Veterinary Hematology for reference intervals for different species of animals. To perform coagulation testing on a variety of animal species one should have an instrument that can measure short and prolonged times in PT, APTT and speciality coagulation assays. Many speciens have vastly different coagulation protein levels than humans. For example rabbits have FV levels starting sometimes at 3,000% activity to start. Make sure your instrumentation and reagents have maximum flexibility.

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