Chapter 13
Canine Donor Selection
Kenichiro Yagi1 and Brandee L. Bean2
1Adobe Animal Hospital, Los Altos, California, USA
2Adobe Animal Hospital, Los Altos, California, USA
Introduction
As our knowledge of transfusion medicine and transfusion-related complications advances, it is becoming evident that not all blood is created equally. Information regarding blood type, methods of blood collection, donor screening for health and bloodborne pathogens, as well as considerations for veterinary blood donors that are not true voluntary donors have all become criteria in donor selection. There are many risks posed to the blood donor and transfusion recipient as donations are collected and transfusions performed. Veterinary professionals participating in transfusion medicine and blood banking should hold themselves accountable to the highest standards during donor selection in order to keep the donors and recipients safe from harm.
Considerations in donor selection
Given that blood is made available through donations from other animals and the demand for blood products is steadily increasing, there is significant pressure placed on the veterinary blood banking community to expand the donor pool as much as possible. This pressure is balanced against the responsibility that veterinary blood banking professionals have to avoid collecting blood from animals unsuitable to donate, which can harm the donor and/or recipient. Blood banking professionals must adhere to strict donor selection criteria in order to prevent this harm (Table 13.1).
Table 13.1 Canine donor screening criteria
| Criteria | Recommendation |
| Age | 1–8 years |
| Weight | >50 lb (22.7 kg) |
| Physical examination | No abnormal findings |
| Complete blood count Chemistry profile | PCV > 40% Results within reference intervals |
| Blood type | DEA 1 positive or negative DEA 4 positive Ideally DEA 3, DEA 5, and DEA 7 negative |
| History | No prior transfusions Not currently taking medication(s) Not currently pregnant |
| Infectious disease screening | Negative for: Babesia spp. Ehrlichia spp. Neorickettsia spp. Leishmania spp. Trypanosoma cruzi Brucella canis Mycoplasma hemocanis (conditional) Bartonella spp. (conditional) Heartworm |
| Preventative medication(s) (if geographically indicated) | Heartworm Flea/tick |
| Behavior/temperament | Calm Not anxious at hospital Trainable |
| Owner | Responsible Reliable Committed |
DEA, dog erythrocyte antigen; PCV, packed cell volume.
Age
One of the first criteria to ensure donor safety is age. A typical age range recommended for canine donors is 1–8 years old. Dogs younger than 1 year old have not yet fully matured and blood loss during this time will negatively affect development. In addition, the cardiovascular system is less resilient to changes in intravascular volume and does not elicit as strong a compensatory response, potentially leading to more severe hypotension and reduced perfusion during blood loss. This makes blood collection during this age a potentially harmful process that should be avoided.
The upper age limit has traditionally been designated as 8 years of age due to the potential decline in the dog’s ability to recuperate from the blood loss or the potential for subclinical underlying disease processes that could be exacerbated during blood collection. Human blood donor criteria in the United States have no upper age limit mandated by the Food and Drug Administration (FDA) or specified by the American Association of Blood Banks (AABB) and many blood centers allow people over the age of 65 years of age to continue donating if they are regular donors and their physician deems them to be healthy enough to do so (Fan et al. 2012). In Canada, people >65 years of age who have not donated during the previous 2 years must obtain a letter from a physician, whereas those >71 years of age must obtain an annual letter (Fan et al. 2012). Animal blood donors are able to donate beyond 8 years of age at the veterinarian’s discretion, given that they show signs of excellent health and no laboratory abnormalities on screening blood work. Retention of healthy donors in the program for a longer period of time will increase the donor pool size and reduce the cost to produce blood products. While there is a higher prevalence of disease in older populations, an effective increase in eligible donors has been seen through extension of the age limit in human blood donors (Fan et al. 2012).
Weight
The donor body weight correlates with the blood volume circulating in the blood vessels. Donors should have sufficient blood volume to donate the desired amount of blood without any detrimental effects. The total blood volume in a dog is approximately 85 mL/kg (80–90 mL/kg) (Jahr et al. 2008). Previous research evaluating the effect of blood donation on arterial blood pressure and other compensatory signs of shock has indicated that while sedated, a 15% blood volume collection resulted in a marked increase in pulse rate compared to 13% blood loss collection in dogs (Ferreira et al. 2015). A similar study performed on unsedated greyhounds documented no adverse effects (e.g., weakness, lethargy, or collapse) during collection of 17–22% of blood volume (Couto and Iazbik 2005). Both studies observed a transient decrease in systolic blood pressure, which remained within normal limits.
Using these numbers, dogs should be able to tolerate a collection volume of 11–19 mL/kg, when using an estimated blood volume of approximately 85 mL/kg. Therefore, dogs that are at least 52 lb (23.6 kg) should be able to tolerate a typical blood collection volume of 450 mL; any further increase in body weight will increase the safety margin of donation. However, a commonly used threshold for a 450 mL donation is 50 lb (22.7 kg), since the upper end of estimated blood volume can be as high as 90 mL/kg in dogs.
The standard donation volume is 450 mL because closed blood collection systems used for component separation in people are of this size. A 250 mL donation can be collected from dogs weighing over 29 lb (13.2 kg) into single-chamber bags available for transfusion of this volume of whole blood. This is less desirable on a routine basis, since the use of these bags limits the ability to practice component therapy.
Calculation of tolerable collection volume is based on lean body weight; fat increases body weight without a significant increase in blood volume. A dog with ideal body condition is described as having easily palpable ribs without excess fat, the waist observed behind the ribs when viewed from above, and the abdomen “tucked up” when viewed from the side. Members of the blood banking team should be familiar with body condition scoring such as that provided by the World Small Animal Veterinary Association (WSAVA) Global Nutrition Committee (Figure 13.1).
Figure 13.1 World Small Animal Veterinary Association body condition scoring chart. These guidelines were first published in Journal of Small Animal Practice, July 2011, 52 (7), 385–396, published by John Wiley and Sons Ltd and are published with permission.
Physical characteristics
The physical characteristics of dogs should also be considered to determine their suitability as a blood donor. Donors should have a physical conformation that will allow easy access to the jugular vein, as well as ease in prepping the area aseptically and maintaining aseptic technique. Donors with jugular veins that are easily accessible and visible or palpable will be more likely to have successful blood collections performed, thus improving the experience for the donor and blood collection team. Dogs with increased skin thickness, underlying adipose tissue, and excess skin folds are preferentially eliminated from the donor pool, especially if repeated difficulties and unsuccessful venipuncture are experienced.
Canine blood types
Blood types are determined by specific red blood cell (RBC) antigens present on the membrane surfaces as an integral glycoprotein and are a source of immunologic complications when not properly matched between the donor and recipient.
DEA system
Canine blood groups currently use standardized nomenclature called the dog erythrocyte antigen (DEA) system. There are seven antigens described in the DEA system: DEA 1, DEA 3, DEA 4, DEA 5, DEA 6, DEA 7, and DEA 8. Of these, DEA 1 is routinely tested for in veterinary practices using readily available commercial kits. The presence of DEA 4 and 7 can be tested through commercial blood typing laboratories. Typing for DEA 3 and 5 is intermittently available through some commercial blood banks. There is very little information regarding DEA 6 and 8, which currently have no typing sera available for testing (see Chapter 9 for more information).
Universal donors
The most desirable blood type in a canine donor is what is considered “universal”, or blood that can be transfused to any canine recipient without the risk of immunologic complications related to blood type antigens. This requires the donor to express the null phenotype for every RBC antigen. Because the only RBC antigens that canine donors can be tested for are DEA 1, DEA 3, DEA 4, DEA 5, and DEA 7, it is presently impossible to find a true universal donor that has tested negative for all known DEAs. In addition, 98–100% of the reported canine population is positive for DEA 4, making finding a donor negative for this DEA virtually impossible (Swisher et al. 1962; Spada et al. 2015). Donors testing negative for DEA 1 are often loosely called “universal donors”, although this is not truly the case. This terminology is used because only DEA 1, DEA 4, and DEA 7 are readily available for testing through commercial laboratories, DEA 4 is positive in virtually all dogs, and a mismatch in DEA 7 does not cause clinically significant immunologic complications. Commercial blood banks that include donors testing negative for DEA 1, DEA 3, DEA 5, and DEA 7 and positive for DEA 4 will appropriately label their RBC products as “DEA 4 positive only”, indicating the presence of DEA 4 and absence of all other DEAs that can be tested for (Figure 13.2).
Figure 13.2 Canine packed red blood cells positive for dog erythrocyte antigen (DEA) 4 and negative for all other testable DEAs (1, 3, 5, and 7).
Other blood groups
In addition to RBC antigens of the DEA system, there are other antigens that are less commonly known. The Dal antigen, first observed to be absent in some Dalmatians and now found to be absent in some Doberman Pinschers and Shih Tzus, is an antigen that is present in most dogs (Blais et al. 2007; Goulet et al. 2014). An RBC antigen characterized by the presence N-acetyl-neuraminic acid or N-glycolyl-neuraminic acid has been described in Asian breeds, including Shiba Inus, causing agglutination when mismatched (Yasue et al. 1978; Hashimoto et al. 1984). Another blood group named the D system comprises D1 and D2 antigens, with the incidence of D1 being higher in the Akita, Shiba, Kishu, and Shikoku (all Japanese) breeds, whereas most North American and European breeds do not express D1 (Ejima et al. 1994). An RBC antigen agglutinated by lectin extracted from Clerodendron tricotomum has been described and designated as type C has and considered separate from the DEAs (Yoshida 1979; Usui et al. 1995).
While our current knowledge on these lesser known and less extensively described antigens is limited and the prevalence of these antigens is infrequent or undetermined, veterinary blood banking professionals should be aware that there is still potential for sensitization to a variety of other RBC antigens when using DEA 1 negative blood.
Desirable blood types
Despite current limitations in the understanding of and testing for RBC antigens, a strategy should be employed that allows for maximizing donor numbers without compromising the safety of recipients. The least immunogenic donor tests negative for every RBC antigen that can be tested for and only positive for antigens that virtually all dogs express. This means that donors testing positive for DEA 4 and negative for DEA 1, DEA 3, DEA 5, and DEA 7 (designated as “DEA 4 positive only”) have the safest blood in terms of RBC antigen incompatibilities, and thus the most desirable blood type. It is important to realize that proper pre-transfusion compatibility testing is still necessary to minimize the chances of harm to the recipient (see Chapter 9).
Blood from canine donors designated as “DEA 4 positive only” is useful for dogs requiring emergency transfusions that cannot wait for blood typing or crossmatching to be performed. In the dogs that can tolerate a delay of a few minutes to at least perform blood typing for the DEA 1 antigen, blood collected from donors that are DEA 1 and 4 positive, but negative for other testable DEAs can be used without concern for recipients positive for DEA 1. Studies evaluating the prevalence of DEA 1 in various canine populations worldwide have indicated 47–55% expression of the antigen (Van der Merwe et al. 2002; Riond et al. 2011; Mesa-Sanchez et al. 2014; Spada et al. 2015). Since approximately half of dogs will be DEA 1 positive, including donors testing positive for DEA 1 will double the number of available canine donors, thus making donors only positive for DEA 1 and DEA 4 also desirable.
While testing all potential canine donors for DEA 1, DEA 3, DEA 4, DEA 5, and DEA 7 is desirable, testing services might be unavailable depending on the practice setting. In that case, donor programs might choose to utilize in-hospital blood typing kits for DEA 1 as their method of canine donor blood typing, with knowledge that omitting testing for the remaining DEAs could lead to immune system sensitization of the recipient if exposed to other antigens and a higher likelihood of delayed hemolysis or incompatible transfusions in the future.
Agglutination card test
In-hospital agglutination card tests (RapidVet-H®, DMS Laboratories, NJ) are available and designed to detect canine DEA 1.1 (see the section on nomenclature of DEA 1). The DEA 1.1 test kit has a DEA 1.1 positive control, negative control, and the test well (Figure 13.3). The test well contains murine monoclonal antibodies against DEA 1.1. Agglutination occurs with antibody–antigen complex formation, indicating that the dog patient is positive for DEA 1.1. The control well serves to identify the presence of auto-agglutination. However, because the test relies on agglutination for blood type detection, interpretation of blood samples obtained from a patient with auto-agglutination are unreliable.
Figure 13.3 DEA 1.1 agglutination test card (image courtesy of DMS RapidVet-H, DMS Laboratories Inc., Flemington, NJ).
Immunochromatographic test
Another available in-hospital blood typing kit utilizes immunochromatography to test for DEA 1 (QuickTEST DEA 1, Alvedia, Limonest, France) (Figure 13.4). This kit uses a porous strip impregnated with antibodies in two locations (Figure 13.5). In the sample area, DEA 1 positive RBCs will form immune complexes with antibodies that are labeled with a chromatographic substance such as colloidal gold or selenium. The RBCs will then pass through the detection area with the antibodies fixed in place, which stops the migration of the RBCs by attaching to them. DEA 1 negative blood will result in one band at the test control area (Figure 13.6), while DEA 1 positive blood will display a second band at the DEA 1 test area (Figure 13.7
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