Providing safe and effective transfusion therapy is essential. Blood typing is clinically important to ensure blood compatibility. This lecture aims to describe blood typing and cross match (XM) techniques and their clinical relevance.

Canine Blood Types

Canine Blood Group System

Blood types are inherited antigens present on the RBCs surface membrane. Previous studies led to the initial international recognition of blood groups termed dog erythrocyte antigens (DEA). DEA 1 is considered the most important blood group in dogs due to its strong antigenicity and nearly equal distribution of DEA 1+ and DEA 1- dogs among many breeds worldwide. New common blood types named Dal, Kai 1 & 2 have been recently described. Currently, canine donors and recipients that have not been previously transfused are considered to have no clinically important alloantibodies and thus are expected to be compatible in a minor and major XM test. However, after transfusion, canine recipients may become sensitized, even when DEA 1 matched, which may lead to blood type incompatibilities recognized by incompatible major XM results, acute haemolytic transfusion reactions, or both. Acute haemolytic transfusion reactions due to blood group incompatibilities between recipient and donor are serious complications, but can usually be avoided when transfusing DEA 1-matched and cross-matched blood in previously transfused dogs.

Canine Blood Typing

In-clinic kits with monoclonal anti-DEA 1 antibodies are available for DEA 1 typing. In contrast, only polyclonal typing reagents are available on a limited basis for DEA 3, 4, and 7. Furthermore, polyclonal or monoclonal typing reagents for Dal and Kai 1 & 2, respectively, have recently been introduced by specific laboratories (i.e., Animal Blood Resource International, USA). The necessity of extended type screening of donors is controversial given the low risk of significant transfusion reactions related to these antigens; however, it may be extremely helpful in understanding cases of XM incompatibility, especially after previous transfusion(s). Moreover, the high prevalence of Dal negative dogs should lead to the development of a specific test for this group.

Blood typing is based on an agglutination reaction, using polyclonal or monoclonal antibodies to react with red cell antigens. When using these antibodies, the presence or absence of agglutination detects the presence (positive) or absence (negative) of the particular red cell antigen being tested respectively.

One of these in-clinic kits using monoclonal anti-DEA 1 antibodies is a rapid test commercialized by Alvedia®. The blood typing Quick Test® uses the technique of immunochromatography. This technology is based on the migration of RBCs on a specially treated paper strip. Monoclonal anti-DEA 1 antibody is incorporated on the strip. It binds to DEA 1+RBCs. This causes a red line to appear in front of the DEA 1 mark. Quick Test® detects all levels of DEA 1 antigen expression, from very strong to very weak. Whatever the intensity of the line, even very weak, the dog is classified as DEA 1+. There is another rapid blood type technique: DMS (CARD), based on an agglutination reaction with a monoclonal anti-DEA1 antibody. Recent studies comparing these techniques showed a good agreement with some differences in dogs with immune-mediated haemolytic anaemia.

Feline Blood Types

Feline Blood Group Systems

The major feline blood group system is known as the feline AB blood group system and contains three types: type A, type B, and type AB (rare). The distribution of these blood types varies geographically. Recent genetic work has determined that mutations in the enzyme, cytidine monophospho-N acetylneuraminic acid hydroxylase (CMAH), are responsible for the B blood type. Cats with type A have N-glycolylneuraminic acid (NeuGc) on their RBC membranes while type B have N-acetylneuraminic acid (NeuAc). CMAH converts NeuAc to NeuGc so lack of this enzyme leads to accumulation of NeuA. Type A cats may have weak anti-B alloantibodies which can cause shortened RBC survival if a B donor is used. Type B cats, however, have very strong anti-A antibodies and can have a fatal reaction from as little as 1 ml of transfused type A blood. Type AB cats have no alloantibodies against either type A or B. They should receive either AB or A blood if they need a transfusion due to the strong anti-A antibodies present in cat B serum.

AB typing of patients and donors is generally recommended to assure A-B compatibility. A-B matched transfusions are required to be effective. In addition, Mik has been proposed as an additional blood group system with potentially naturally occurring alloantibodies in some Mik-cats. Most cats have this antigen but in cats who do not, naturally occurring antibodies can be present which can lead to a haemolytic transfusion reaction with an initial incompatible transfusion.

Feline Blood Typing

There are now two commercially available in-house typing kits for cats (Rapid VetH Feline, DMS laboratories, NJ [CARD] and Quick Test A+B, Alvedia, France [CHROM]). Both kits use monoclonal antibodies against type A and type B. In a recent study comparing typing methodologies in cats, a gold standard tube agglutination, CARD and CHROM gave identical results in 52 of 58 cats. CARD had overall accuracy of 91.4% and CHROM had overall accuracy of 94.8%. In 2 of the 6 cats with discordant resultants, FeLV infection was present. It is recommended that B and AB cats be confirmed by a second method or through an outside laboratory. There is currently no in-house typing system for Mik.

Cross-Matching

Cross-matching determines the serological compatibility between patient and donor bloods, based on an agglutination reaction, allowing detection of preformed alloantibodies (cats) or previous sensitization (dogs and cats). The major XM is an assessment of the compatibility between the donor RBC and patient plasma/serum, with the minor XM being the opposite (donor plasma/serum and patient RBCs). Minor XM incompatibilities are mostly of concern when large volumes of plasma or whole blood are to be administered. Patient auto-agglutination or haemolysis may result in incompatibility and a control should be run with the patient RBCs and patient serum. Auto-agglutination or severe haemoglobinemia precludes testing. Washing the blood three times with physiologic saline may disperse auto-agglutination and “rouleaux” formation.

Some use the immediate-spin XM. This technique employs a 3- [sic] to percent suspension of donor red cells suspended in saline, with 2 drops of recipient serum, centrifuged at 3400 rpm for 15 seconds (Serofuge, Sorvall, Wilmington, DE).

Major and minor XM testing is offered by clinical pathology laboratories which use the standard tube, microtiter plate, or neutral saline gel column method without canine antiglobulin at either room temperature or 37°C. Because of the need for washing RBC and the involvement of several steps, XMing of dogs and cats is rarely done in veterinary practice. A gel tube-based XM kit has been available for in-clinic use. Moreover, an antiglobulin-enhanced immunochromatographic strip kit, similar to the direct antiglobulin test (DAT), recently has been introduced for XMing dogs. A recent study (Goy-Thollot et al. 2017) showed that the antiglobulin-enhanced immunochromatographic strip kit as well as the antiglobulin-enhanced gel column technique are practical tests for XMing in the clinic and laboratory, respectively.

Cross-Match in Dogs

Since dogs do not have naturally occurring alloantibodies, the initial XM between a dog which has never been transfused and his donor should be compatible. Acute haemolytic transfusion reactions and incompatible XMs have been reported clinically in previously transfused dogs receiving a transfusion ≥4 days after the first transfusion. However, documentation of post-transfusion alloimmunization by a major XM test is sparse, and the RBC antigen specificity is rarely if ever identified in any transfused dog. In a recent study (Goy-Thollot et al. 2017), the antiglobulin-enhanced immunochromatographic strip kit as well as the antiglobulin-enhanced gel column technique identified alloantibodies on RBCs of some transfused dogs (44%). This high post-transfusion alloimmunization rate by a major XM test leads to warrant major XM in any dog that previously had received DEA 1-matched RBC before the next transfusion.

XM in Cats

In case AB typing is not available as well as in previously transfused cats, major and minor XMs are recommended. XMing cats is technically restricted by the difficulty to obtain blood from recipient and donor cat prior to transfusion, limited availability of standardized XM protocols, and lack of any in-clinic kits for XMing cats.

RBC incompatibilities may be present in transfusion-naive cats which could justify the recommendation to perform a major XM before all (including the first) RBC transfusions in cats in a non-emergent setting. However, one could argue that XMing all cats would result in additional cost and unnecessary delay in time to transfusion. Although the clinical relevance of major XM incompatibilities detected in transfusion-naive cats is unknown, previous documentation of anti-Mik RBC alloantibodies causing acute haemolytic transfusion reactions in transfusion-naïve cats suggests erring on the side of caution. Future prospective studies evaluating the effect of XM on transfusion efficacy in cats are warranted.

References

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