An Accurate Blood Test for Pregnancy Diagnosis in Dogs

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Pregnant Dog

Is my dog pregnant?

As much as veterinarians would like to give a definite answer to this question, we have not always been able to. An accurate, easily accessible test was needed for pregnancy diagnosis. Traditionally, pregnancy diagnosis has been by palpation of the bitch between 22nd and 28th day after breeding. But, unless the bitch was thin and very cooperative, even the most experienced veterinarian could often only say, “I think so.” rather than, “Yes, she is.” X-rays are more definitive, but only after day 40. Ultrasonography, as alternative to palpation, often involves referrals to a distant location and imposes greater expense.

The first pregnancy test for women, based on the erythocyte sedimentaion rate(ESR), was developed by Robin Fahraeus in 1918. With the advent of more specific tests based on human chorionic gonadotropin (HCG), ERS for pregnancy indication faded into the past. Fahraeus did not realize it, but it was an increase in the fibrinogen during pregnancy that caused the ESR to increase, maybe it could be used as a pregnancy test for dogs. In 1991, Allan HartBVSc, Robert Levine M.D. and Steven Wardlaw M.D. developed accurate, repeatable heat precipitation fibringoen as part of the quantitative buffy caot(QBC) analysis technology. In 1997, the fibrinogen parameter was added as part of the QBCVetAutaread (Idexx Laboratories). Using this technology, which is now available in many veterinary clinic laboratories, Allan Hart began researching pregnancy diagnosis in dogs. Fibrinogen proved to be a reliable marker for pregnancy when measured by a precise and reproducible method. Increase of over 300 ug/dL (from a normal of 100-250 ug/dL) between days 28 to 30 of gestation, in healthy bitches are positive for pregnancy. False negatives may be seen in large breed dogs with single puppy litters. But, even in these cases, a significant increase in fibrinogen between a prebreeding and a 28 to 30 day post breeding level would be diagnostic.

In conclusion, measuring firinogen levels over 300 ug/dL, using the Idexx QBC VetAutoread, at 28 to 30 days postbreeding, is positive for pregnancy in bitches.


A Rapid, Accurate IN-House Pregnancy Test for Dogs, By: Dr. Allan
H. Hart B.V.Sc, Veterinary Forum, August 1997.

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