Blood typing and crossmatching; What you don't know may hurt you (Proceedings)

Introduction

The goals of this session are to provide some information related to blood types, blood typing, crossmatching, and to relate a few case examples that emphasize the usefulness of knowing what you may be working with. The focus will be on dogs and cats, but horses will be discussed as well.

Blood types are classifications of heritable species-specific antigens comprised of proteins, lipids, and/or carbohydrates (glycolipids, glycoproteins). Other cells, as leukocytes, platelets or other tissues may also share these antigens. Rarely, antigens are shared between species. Alloantibodies (or isoantibodies) are antibodies present in the serum against an antigen from another animal of the same species. These may be naturally acquired or induced through previous exposure as with transfusion.

Canine blood types and antibodies

Dog blood types are known as the Dog Erythrocyte Antigen System (DEA) and are numbered. DEA 1 was formerly known as "A" and consists of 4 alleles: negative, 1.1, 1.2, and 1.3. DEA 1.1 and DEA 1.2 are the most important antigens and together comprise approximately 60% of the canine population. Both of these types are considered "A positive", however type DEA 1.2 dogs, which comprise 7-29% of the canine population, will develop potent anti-DEA1.1 antibodies once transfused with DEA 1.1 cells. Naturally occurring antibodies to these antigens are generally considered nonexistent. First time transfusions may be associated with a decreased circulating lifespan of the transfused cells and subsequent transfusions will be associated with an acute hemolytic reaction. DEA 1.3 is only known to exist in German shepherd dogs from Australia.

DEA 4 comprises up to 98% of the general dog population but only ~75% in Doberman Pinschers. Dogs with this type alone are considered "universal donors". Naturally occurring DEA 4 antibodies are not known to exist. DEA 3 and 5 are expressed in lesser proportions of the dog population, but greyhounds tend to have upwards of 23% and 30% of DEA 3 and 5, respectively. DEA 7 is present in 8-45% of the population. Naturally occurring antibodies have been observed against these antigens with a delayed transfusion reaction causing decreased lifespan of transfused cells but no hemolysis. Dal is a high frequency antigen reported in 2007 that is lacking in ~20% of dalmations tested (5/25). IgG antibodies apparently developed by 40 days after transfusion; 55 non-dalmation donors were all incompatible at this time. Incompatible transfusions involving this antigen could result in acute and delayed hemolytic reactions. Little is known about DEA 6, 8 and ~11 other antigens thought to exist. Typing sera for these antigens are not available.

Cat blood types and antibodies

Only the "AB" system in cats has been routinely recognized to date and consists of three types: A, B, and AB. Type A is the most common and comprises over 95% of the general domestic shorthair/longhair population in the United States. Type B is more common in certain breeds: up to 10% of Maine coon and Norwegian Forest; up to 20% of Abyssinian, Birman, Persian, Somali, Sphinx, and Scottish Fold; and up to 45% of Exotic and British Shorthair, Cornish Rex and Devon Rex. It has not been observed to date in Siamese, Burmese, Tonkinese, Russian Blue, American Shorthair and Oriental Shorthair.

Type AB has been observed in the domestic shorthair as well as breeds known to have Type B. This blood system follows simple Mendelian inheritance with the A (A) gene having dominance over the AB (ab) gene which has dominance over the B (b) gene. Type A cats may have any one of three phenotypes: A-A, A-ab, or A-b. Type AB cats may have either ab-ab or ab-b phenotypes, and a type B cat can only have the b-b phenotype. Therefore, a breeding pair of Type "A" cats can produce kittens of Types A, AB or B, depending on their phenotypes.

Cats have naturally occurring antibodies. All type B kittens develop antibodies within a few weeks after birth and high titers develops around three months of age. Type A kittens will also develop antibodies, but these are generally considered less potent. Since antibody can be transferred to the kitten via the colostrum up to 16 hours after birth, kittens born healthy can suddenly "fade" from the hemolytic anemia that develops. This generally occurs in type A or AB kittens born to B queens. Type AB cats are considered to be universal recipients as they will lack anti-A and anti-B antibodies, however they should be transfused with type A cells to avoid inadvertently transfusing potent anti-A antibodies from a type B donor. This would be an example of a "minor-side" reaction (see minor crossmatch info below)..

A new antigen, "Mik",was reported in 2007 and is present in a high number of DSH cats. Those lacking the antigen (~6% of those tested) have the potential to develop an acute hemolytic reaction after transfusion of AB matched blood. This emphasizes the importance of crossmatching all cats prior to transfusion.

Horse blood types

Horses have a very complex system comprised of 8 blood groups (A, C, D, K, P, Q, U, and T) and at least 32 antigens for approximately 400,000 possible combinations. As a result, and due to the lack of commercially available typing sera, blood typing is not performed. Naturally occurring antibodies exist against the Aa and Qa types and these are very immunogenic. Crossmatching can be performed, but even if compatible, the half life of transfused cells is only about 2-6 days. As the antigens vary in frequency by breed, it is helpful to locate same-breed donors for crossmatching.

Blood typing and crossmatching

Freshly collected blood in EDTA and a clot tube from both the recipient and donor are recommended for typing and crossmatching unless the donor has been previously screened for antibodies in which case only cells are needed. Alternatively, tubing segments or "pigtails" may be used from the donor unit as long as sterility of the unit remains intact. The samples should be free of hemolysis and lipemia whenever possible.

Commercial blood typing kits are available for dogs and cats and can be used to screen potential donors, and make appropriate selections for crossmatches and transfusions based on recipient blood type. Examples of typing kits include typing cards (DMS Laboratories, In., Flemington, NJ), a gel column diffusion assay (DiaMed, Switzerland) and an immunochromatographic cartridge (Alvedia, France). All kits type for DEA 1.1 only in dogs and for A, B and AB in cats. Potential All are relatively simple methods and include a means of performing an auto control to identify potential interference from autoagglutination. The gel column requires the use of a centrifuge specifically designed to hold the columns and a total of ~20 minutes to run the procedure. As no method is perfect, the user should thoroughly read package inserts for sources of potential erroneous results and follow the instructions exactly. Confirmatory testing of permanent donors, questionable results, or in lieu of in-house typing for elective surgeries can be performed by outside laboratories such as Animal Blood Resources International, Stockbridge, MI (877-517-6227) or the University of Pennsylvania Hematology and Transfusion Laboratory (215.573.6376) for dogs and cats and to the Veterinary Genetics Laboratory (Davis, CA) for typing (530-752-2211)horses.

The major crossmatch (XM) tests for detectible of naturally occurring or induced antibodies in the recipient serum against donor erythrocytes. This should be done any time a patient likely to have strong naturally occurring antibodies, if the transfusion is history is unknown, or if there has been a history of prior transfusion at least 2-4 days previously, even with the same donor. Crossmatch kits are available from DMS Laboratories, inc. and DiaMed. The minor crossmatch tests for detectible levels of antibodies are present in the donor plasma against the patient erythrocytes. While generally considered less important, occasionally significant reactions have occurred. Permanent donors can be selected based on commercially offered blood typing and screening for antibodies in order to minimize the chance of a minor-side reaction. The typing and crossmatch kits typically provide a means of running controls to rule out false positive reactions due to autoagglutination or claim no interference from it.

A very crude method of crossmatching that should be reserved for emergency situations only is the slide crossmatch. The major crossmatch consists of mixing two drops of recipient plasma with a drop of blood from the donor at room temperature on a clean glass slide and observing for agglutination while rotating the slide for one minute. A minor-side crossmatch can be performed in the same way using 2 drops of donor plasma and 1 drop of recipient blood. Potentially fatal hemolytic reactions may be missed as hemolysis is difficult to recognize by this method.

Algorithm

An algorithm is provided to assist with deciding when to type and crossmatch dogs in order to minimize transfusion reactions and sensitization to transfused blood.

      A.    Has the dog been previously transfused?

                a) Yes (or Unknown) go to step B.

                b) No Go to step C.

      B.    Has it been ≥ 4 days since the transfusion?

                a) Yes/Unknown Crossmatch in order of availability: Universal Donor, DEA 1.1 negative or type-matched blood, DEA 1.1 negative or type-matched siblings, DEA 1.1 negative or type-matched same breed.

                b) No Go to step C.

      C.    Is a repeat transfusion likely in ≥ 4 days?

                a) Yes Transfuse in order of availability: Universal Donor, DEA 1.1 negative or type-matched blood.

                b) No Go to Step D.

      D.    Is recipient DEA 1.1 positive?

                a) Yes Transfuse DEA 1.1 positive or negative blood.

                b) No/Unknown Transfuse DEA 1.1 negative blood.

References and suggested reading

Weingart C. Giger U. Kohn B. Whole blood transfusions in 91 cats: a clinical evaluation. J Feline Medicine & Surgery. 6(3):139-48, 2004 Jun.

Brown D, Vap L. Principles of Blood Transfusion and Crossmatching in Thrall MA, ed. Veterinary Hematology and Clinical Chemistry, Lippincott, Williams and Wilkins, Philadelphia, 2004:197-207. (new edition pending)

Melzer KJ. Wardrop KJ. Hale AS. Wong VM. A hemolytic transfusion reaction due to DEA 4 alloantibodies in a dog. JVIM 17(6):931-3, 2003

Lanevschi A. Wardrop KJ. Principles of transfusion medicine in small animals. Canadian Vet J 42(6):447-54, 2001 Jun.

Griot-Wenk ME. Callan MB. et al w/ Giger U. Blood type AB in the feline AB blood group system. AJVR. 57(10):1438-42, 1996 Oct.

Callan MB. Jones LT. Giger U. Hemolytic transfusion reactions in a dog with an alloantibody to a common antigen. JVIM 9(4):277-9, 1995 Jul-Aug.

Harrell KA. Kristensen AT. Canine transfusion reactions and their management. VCNA - Small Animal Practice. 25(6):1333-64, 1995 Nov.

Hale AS. Canine blood groups and their importance in veterinary transfusion medicine. VCNA - Small Animal Practice. 25(6):1323-32, 1995 Nov.

Griot-Wenk ME. Giger U. Feline transfusion medicine. Blood types and their clinical importance. VCNA - Small Animal Practice. 25(6):1305-22, 1995 Nov.