THE DAL ANTIGEN
In 2007 , Blais et al . ( 2007 ) suspected a new RBC antigen not yet described in veterinary medicine , as a result of a dalmatian developing specific antibodies due to a sensitisation of unknown origin during an initial transfusion . The new antigen was named the Dal antigen . Blais et al . ( 2007 ) theorised dalmatians to be the only breed to test negative for the Dal antigen and predisposed to acute transfusion reactions if transfused blood from a Dal-positive donor .
This theory was recently disputed by Goulet et al . ( 2017 ) in a clinical trial that set out to determine the mode of inheritance and prevalence of the Dal antigen among other dog breeds in North America . Their study consisted of 1,130 dogs : 128 dalmatians , 432 dobermanns , 21 shih tzus and 549 dogs of other breeds . This was an extremely sizeable sample , representing a large number of breeds to eliminate the risk of chance on concluding results ( Crombie , 1996 ). The results found an increased incidence of dalmatians ( 12 %), dobermanns ( 42 %) and shih tzus ( 57 %) testing negative for the Dal antigen . Furthermore , three of the 122 mixed-breed dogs also tested negative . Sex , coat colour and DEA 1 status did not have any effect on the Dal status of the patient . However , within this study , geographical area did vary , in particular with dobermanns , which coincides with an additional discovery by Goulet et al . ( 2017 ) of the Dal antigen being of a dominant inheritance .
The Goulet et al . ( 2017 ) study raised some challenges relating to Dal-negative blood donors , of which RVNs should be cautious . First , of the 1,130 dogs tested within the study , 228 of them were already enrolled on a blood donation programme . However , 227 of the 228 dogs tested positive for the Dal antigen , making them unsuitable donors for Dal-negative patients . Second , none of the core breeds testing negative for the Dal antigen ( dalmatians , dobermanns and shih tzus ) make ideal candidates for blood donating , due to either their size , temperament or predisposition to diseases such as von Willebrand disease and cardiomyopathies . Therefore , blood banks and veterinary practices may find it difficult to recruit Dal-negative blood donors , amplifying the risk of these patients developing acute transfusion reactions at subsequent blood transfusions if not cross-matched beforehand .
There are currently no in-house blood-typing test kits available for the Dal antigen so , for the safety of a patient receiving successive transfusions , cross-matching is highly recommended . This is supported by the Goulet & Blais ( 2018 ) clinical study , which set out to better characterise anti-Dal antibodies in terms of their rate of production and agglutination titres following sensitisation . Two Dal-negative beagles received a unit of Dal-positive blood . Post transfusion , one of the dogs developed antibodies against the Dal antigen after 21 days , the other after only 4 days . This supports current recommendations ( Pet Blood Bank , 2021 ) to crossmatch patients a minimum of 4 days after receiving a transfusion in order to detect levels of antibodies sufficient for a cross-match result that is as accurate as possible . Neither of the two beagles displayed signs of a transfusion reaction . However , immune-mediated transfusion reactions are rarely seen during the first transfusion , due to dogs not possessing naturally occurring blood antigen antibodies ( Hohenhaus , 2004 ), so a reaction was unlikely to be seen . To determine the real clinical effect of developing antibodies to the Dal antigen in these beagles , it would require a second transfusion to be given . However , this would be unethical due to the theorised risk based on previous blood antigen-antibody related transfusion reactions .
Further research is required to study the genuine clinical significance of Dal antibodies and their risk of provoking a transfusion reaction . However , as RVNs , we must promote the new evidence found in the field of canine transfusion medicine and negate the use of the term ‘ universal donor ’ as this is no longer true . RVNs involved in administering PRBCs should be aware of breeds that may be more susceptible to blood transfusion reactions , due to the formation of blood antigenantibody complexes .
KAI 1 AND KAI 2 ANTIGENS
In addition to the Dal antigen , two new RBC antigens – Kai 1 and Kai 2 – are currently being investigated in regard to their clinical importance . Again , this is after the development of an unanticipated blood-transfusion reaction . Much like the Dal antigen , no commercial test kits are yet available to test for Kai 1 or Kai 2 , and therefore cross-matching is strongly recommended . The ongoing improvement in technology will ultimately result in more erythrocyte antigens being discovered , which only amplifies the necessity for RVNs to keep up to date with evidence-based research to ensure they provide the best care to their patients .
Storage and handling
The integrity and efficacy of a unit of PRBCs is reliant on the holding temperature , aseptic handling during storage and the age of the unit post donation ( Mansell & Boller , 2016 ) ( Figure 3 ). Currently , canine PRBC units are stored for up to 42 days . This is in accordance with human-medicine guidelines from the US Food and Drug Administration ( FDA ) because , at present , there are no legal stipulations on storage duration for canine PRBCs in the UK ( Obrador et al ., 2015 ). Refrigeration of PRBC units reduces the rate of RBC metabolism . This can increase the length of storage time by reducing RBC fragility and decreasing bacterial growth ( Kisielewicz , 2016 ). The risk of bacterial contamination in human PRBC products is low , but donor bacteraemia and contamination during processing and storage has been documented ( Hillyer et al ., 2003 ).
44 Veterinary Nursing Journal