Fast facts about blood typing and crossmatching

Canine Blood Types: 

  • There are at least 13 blood types in dogs as well as the Dal antigen.  The most important canine blood type is dog erythrocyte antigen 1.1 as DEA 1.1 incompatibility results in severe hemolysis. 

  • Dogs don’t have preexisting alloantibodies and pregnancy does not result in antigen sensitization.  In short, a dog can receive a first-ever transfusion without a crossmatch. 

  • All dogs should be typed and ideally, type specific blood products should be utilized (ie. 1.1 positive dog receives 1.1 positive blood).  In practice, many hospitals only stock DEA 1.1 negative blood since both DEA 1.1 positive and DEA 1.1 negative dogs can receive it safely. There is often a national shortage in DEA 1.1 negative blood products and stocking both positive and negative units conserves resources. 

  • It takes 4-5 days for antibodies to develop after a transfusion so for EVERY subsequent transfusion (>5 days after a transfusion), a major and minor crossmatch is necessary to prevent a potentially fatal transfusion reaction. 

Feline Blood Types: 

  • Cats have either type A, type B or less commonly type AB blood. Some cats also lack the Mik antigen, a minor RBC antigen, and can develop hemolytic transfusion reactions even with blood type (A or B) specific blood. 

  • Cats DO have preexisting alloantibodies, therefore, all cats require blood typing before transfusion.

  • While there is controversy about how important a crossmatch is before feline transfusion, a major crossmatch, at minimum, is a good standard of practice to ensure that there is a lower probability of severe transfusion reaction. 

  • It takes 3-4 days for antibodies to develop in cats, a bit quicker than in dogs, so for EVERY transfusion (>3-4 days after a transfusion), a major and minor crossmatch is necessary to prevent a potentially fatal transfusion reaction.  

Crossmatch Simplified

  • Major Crossmatch: Donor RBC and patient plasma 

    • “major component of transfusion = donor RBC”

  • Minor Crossmatch: Donor plasma and patient RBC 

    • “minor component of transfusion = plasma antibodies in the unit” 

  • Crossmatches can be completed immediately in-hospital using gel-based crossmatch kits or can be submitted to a reference lab or animal blood bank if there is not an emergent need. 

  • Patients with autoagglutination can not be crossmatched in-hospital until a RBC wash is completed to “remove” the RBC Ag:AB complexes and therefore eliminate the agglutination.   

Transfusion Trigger:

There is no HCT or PCV number that serves as a “transfusion trigger.”  Physical examination remains the single best diagnostic tool.  Clinical evidence of decreased oxygen delivery to the tissues include tachycardia, tachypnea, weakness and hyperlactatemia. These signs of hypoxia will be evident with even mild-moderate anemia in acutely anemic patients, whereas a PCV of 10-15% may be tolerated in patients with chronic anemia.  

If you have anemia questions or want more great tips, check out DVM Stat

Dr. Kristin Welch

Dr. Kristin Welch is the founder of DVM STAT Consulting. Her love of teaching, passion about all things veterinary medicine, and dedication to the field of Emergency and Critical Care led to DVM STAT Consulting - a platform for education that reaches far wider than was previously possible. Dr. Welch loves solving complicated cases, decoding clinical data and most of all, helping her veterinary colleagues succeed in their drive to provide the highest caliber medicine possible to their patients.  

A 2005 graduate of Michigan State University College of Veterinary Medicine with Honors, she received the Small Animal Clinical Proficiency Award and the Wade O. Brinker Orthopedic Surgery Award.   Following an Internship in Medicine and Surgery at University of Pennsylvania in 2006, she completed a residency in Emergency and Critical Care at Tufts University in 2010.  She is a Diplomate of the American College of Veterinary Emergency and Critical Care.  Dr. Welch relocated after residency to Charleston, SC where she helped grow the Southeast’s first VECCS Level I Emergency and Critical Care certified hospital as the Chief of Emergency and Critical Care.  

Dr. Welch has an equal love for Internal Medicine and ECC. She has a strong interest in trauma and fluid resuscitation, transfusion medicine, and metabolic and respiratory emergencies.  She is proficient in mechanical ventilation, dialysis, and interventional procedures including tracheal stent placement.   She provides diagnostic abdominal, thoracic and cervical ultrasound services and enjoys upper GI endoscopy and endoscopic foreign body retrieval.  

Dr. Welch has been an active lecturer since 2006 and loves teaching.  She has been an adjunct lecturer for the Veterinary Technology program at Trident Technical College. She also teaches internationally though the online platform VetScope. She has published in the Journal of the Veterinary Emergency and Critical Care Society, the Journal of Feline Medicine and Surgery and Clinical Veterinary Advisor.  

Dr. Welch is a busy mom of 3 and her most favorite moments are the stolen quiet moments snuggling with her kids or watching them run and play on the beach.  If she isn’t working, she is running or working out, walking on the beach or planning her next wildlife viewing travel adventure. Wildlife and nature photography is her passion.  She is often found carrying her camera to capture the perfect shot – before the moment passes by.

https://www.dvmstat.com
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