Journal Watch: Veterinary Evidence Based Medicine

I can’t count on my hands the number of times I have uttered the words “I need to look up the current evidence for ….”. The world of veterinary medicine and veterinary research changes on a monthly basis, if not daily and keeping up with the current thoughts or trends in medicine can be challenging, especially in private practice.

Evidence based medicine (EBM) has been practiced since the mid-19th century but in the 90’s really started to become common practice in the medical (human) community. Like all things veterinary medicine, such practices have slowly trickled down from physicians to veterinarians. EBM is the conscientious and judicious use of current best evidence in making decisions about the care of individual patients. The practice of EBM means integrating individual clinical expertise with the best available clinically relevant research. To quote David Sackett a leader in EBM research “Good doctors use both individual clinical expertise and the best available external evidence, and neither alone is enough”.

The difficulties that veterinarians face in keeping up-to-date of all the medical advances reported on a monthly basis are obvious when you think of the number of veterinary journal articles published each month and the time it would take each day to read said articles. Of coarse that is on top of seeing a patient every 15 minutes, performing dental procedures or other surgeries, making call backs and maybe even having a moment to each lunch (we all know that doesn’t happen).

Part of my job as a veterinary internist at our Toronto clinic is to do my best to practice EBM to the best of my abilities and extend such knowledge and information to the referring veterinarians I work with on a daily basis. I am often asked to discuss the latest research or trends in veterinary internal medicine and so I thought that this Blog would be a great way to start. Once a month I am going to post a journal article from one of the primary veterinary journals that I think is clinically relevant and will help us all to practice EBM. I will include the pubmed number so the articles can be searched on line and any feedback, questions or comments can be emailed to me at ctvrc@live.ca.

A Retrospective Study of 1,098 Blood Samples with Anemia from Adult Cats: Frequency, Classification, and Association with Serum Creatinine Concentration

E. Furman, E. Leidinger, E.H. Hooijberg, N. Bauer, G. Beddies, and A. Moritz. J Vet Intern Med 2014;28:1391–1397 Pubmed ID: 25274437

Frequency and classification of anemia in terms of regeneration status and erythrocyte indices are not well described in cats.This retrospective study was performed to determine frequency and regenerative status of anemia in samples from adult cats, to assess the sensitivity and specificity of macrocytosis and hypochromasia for detecting regenerative anemia (RA). Laboratory records from 30,503 blood
samples from cats between 2003–2011 in Vienna Austria.

Overall, 1,098 cats with anemia were documented. 57.7% were classified as nonregenerative (NRA) and 42.3% as regenerative. RBC, Hematocrit, and Hemoglobin were significantly lower in the RA compared to NRA group. Sensitivity and specificity of the combined high MCV and low MCHC to detect samples with RA were 19.5 and 90.7%.

Majority of anemic samples were classified as NRA. Anemia was more severe in cats with RA. Erythrocyte indices MCV and MCHC were not sensitive indicators of RA. Interestingly, there were even a small proportion of samples with macrocytic hypochromic morphology in the NRA
group, although this morphology typically is associated with RA. Regeneration status must be determined by a reticulocyte count because erythrocyte morphology and the erythrocyte indices MCV and MCHC are not reliable criteria for differentiation of RA
from NRA in cats.

Although this study has some limitations I feel that it is a good evaluation blood samples from such a large population of cats coming from primary practices. Almost 4% of all samples submitted had some degree of anemia, reflecting its common occurrence in our feline pet population.

In veterinary medicine it is common place to describe anemia based on the hematocrit (Ht). However, based on human and veterinary literature hemoglobin (Hb) seems to be the analyte most resistant to variability and considered by some authors to be a better indicator for diagnosing anemia. As such I would encourage all clinicians to use all three variable: Hb, Ht and red blood cell count when evaluating the erythron.

The take away from this study is that you must perform a reticulocyte count to correctly identify the nature of the anemia in cats.

Reviewed by Michael Goldstein, DVM, Diplomate ACVIM

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