Prospective evaluation of the utility of cross-matching prior to first transfusion in cats: 101 cases

Retrospective evaluation of plasma transfusions in dogs undergoing general anaesthesia: 85 cases (2017-2021)

OBJECTIVE

To describe the use of plasma transfusion in anaesthetized dogs, specifically the triggers for use, the population administered plasma, reported adverse events and human errors associated with transfusion.

STUDY DESIGN

Retrospective observational study.

ANIMALS

A total of 85 client-owned dogs.

METHODS

A search of electronic transfusion and anaesthetic records at a university teaching hospital was performed to identify dogs administered plasma during the study period (January 2017 to June 2021). Data collected included signalment, surgical procedure, intraoperative triggers for transfusion, the type of plasma, rate of transfusion and the presence of transfusion reactions, human errors or deviation from transfusion guidelines.

RESULTS

During this period, 85 dogs were administered plasma. Sepsis was diagnosed in 49/85 (58%) dogs, with 42/85 (49%) animals undergoing surgery for septic peritonitis. Perianaesthetic hypotension contributed to the decision to administer plasma in 67/85 (79%) dogs. In 33/85 (39%) dogs, hypotension was the only reason for transfusion, while 31/85 (36%) had other influencing factors, most commonly hypoproteinaemia. Fresh frozen plasma was administered in 95% of cases. Only 31% of transfusions were started at a slower 'test dose' rate and 79% of dogs administered boluses of plasma. No definite, probable or possible transfusion reactions were identified using current veterinary guidelines.

CONCLUSIONS AND CLINICAL RELEVANCE

Plasma transfusions were commonly administered to dogs presenting with sepsis for haemodynamic optimization. Clinicians often chose to bolus plasma instead of initiating transfusions at the recommended initial slow starting rate. No transfusion reactions were identified; however, some reactions may have been masked by the effects of general anaesthesia and/or have been difficult to recognize in this critically ill canine population.

Identification of feline erythrocyte antigen 6 and lack of alloimmunization to feline erythrocyte antigen 4 in cats

BACKGROUND

New feline erythrocyte antigens (FEAs) have been described based on the presence of naturally occurring alloantibodies (NOAb), but their immunogenicity and clinical relevance are poorly understood.

HYPOTHESIS/OBJECTIVES

Describe the immunogenicity of FEA 4 after sensitizing FEA 4-negative cats lacking NOAb and characterize anti-FEA 4 alloantibodies produced, including their rate of appearance, agglutination titer, and immunoglobulin class.

ANIMALS

Nineteen healthy type A cats were blood typed for FEAs 1 to 5 to identify suitable donor-recipient pairs for FEA 4 sensitization.

METHODS

Four FEA 4-negative cats were transfused with FEA 4-positive red blood cells. Using a gel column technique, posttransfusion samples were screened daily for a week, weekly for a month, and monthly thereafter for anti-FEA 4 alloantibodies.

RESULTS

Alloantibodies were not detected in the first 3 recipients despite repeated transfusions (1 and 3 additional transfusions for 2 and 1 recipients, respectively). In the 4th recipient, alloantibodies against its donor red blood cells were detected 21 days postsensitization. However, they were not directed against FEA 4, but rather against a novel FEA not yet described. The alloantibodies, named anti-FEA 6, remained detectable for >4 months after sensitization and were determined to be mostly immunoglobulin M based on sulfhydryl treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

Feline erythrocyte antigen 4 does not appear to be immunogenic because repeated sensitization of 4 cats failed to produce detectable anti-FEA 4 alloantibodies. A new immunogenic antigen, named FEA 6, has been discovered, but additional studies are needed to document its clinical importance.

Retrospective study of canine blood xenotransfusion compared with type-matched feline blood allotransfusion to cats: indications, effectiveness, limitations and adverse effects

OBJECTIVES

Xenotransfusion is the transfusion of blood from one species to another. With varying availability of allogenic feline blood (AFB) and in emergency conditions, circumstances occur when canine blood is transfused to cats. This study aimed to characterise the indications, effectiveness, limitations, and acute and late transfusion-related adverse effects of canine blood xenotransfusion compared with matched AFB to anaemic cats, and their survival and longer-term outcome.

METHODS

This retrospective study (2013-2020) examined cats receiving canine blood xenotransfusions or AFB.

RESULTS

The study included 311 cats (xenotransfusion [X-group], n = 105; allotransfusion [A-group], n = 206). Xenotransfusion was more frequent among cats sustaining haemorrhage than in those with haemolysis (P <0.01) or hypoproliferative anaemia (P <0.001). Financial constraints were the most common reason to elect xenotransfusion (49%). The post-transfusion mean packed cell volume was higher (P <0.001) in the X-group (22%) compared with the A-group (18%), and also higher (P <0.001) at 48-96 h post-transfusion (23% vs 18%, respectively). Transfusion-related adverse effects (TRAEs) were more frequent (P = 0.001) in the X-group (37.1%) compared with the A-group (19.4%), as were delayed haemolytic transfusion reactions (85% vs 42.5%, respectively; P <0.001). Acute transfusion reactions (ATRs) were more frequent (P <0.001) in the A-group (60%) compared with the X-group (20%). TRAEs were unassociated with survival to discharge. The survival to discharge rate of the X-group (55%) was lower (P = 0.007) than in the A-group (73%), while post-discharge survival rates to 30 days of cats surviving to discharge were 90% and 88%, respectively (P = 0.85).

CONCLUSIONS AND RELEVANCE

Canine blood xenotransfusions to cats might save lives in emergency conditions when AFB is unavailable or blood typing is infeasible. The survival to discharge rate of the X-group was lower than that of the A-group. The longer-term survival rate of cats administered xenotransfusions and surviving to discharge from the hospital was good.

Characterization of post-transfusion anti-FEA 1 alloantibodies in transfusion-naive FEA 1-negative cats

Objectives

The aim of this study was to characterize anti-feline erythrocyte antigen (FEA) 1 alloantibodies following sensitization of FEA 1-negative cats, including their rate of appearance, agglutination titer over time and immunoglobulin class. A secondary aim was to obtain polyclonal anti-FEA 1 alloantibodies to increase the availability of FEA 1 blood typing. We also describe a case study documenting an acute hemolytic transfusion reaction in a transfusion-naive FEA 1-negative feline patient that received FEA 1-positive blood.

Methods

In this prospective clinical study, 35 cats with blood group type A underwent extensive blood typing for FEA 1–5. Two cats were identified as FEA 1-negative; these cats were transfused uneventfully with 50 ml of FEA 1-positive, but otherwise compatible, packed red blood cells. Post-transfusion blood samples were collected routinely as long as anti-FEA 1 alloantibodies were detected. Appearance of anti-FEA 1 alloantibodies was detected using a gel column crossmatch method.

Results

Anti-FEA 1 alloantibodies were detected as early as 5 days post-transfusion and remained detectable for over 400 days in one cat. Agglutination titers in both cats were relatively weak (1:1 to 1:8). The main immunoglobulin class was IgM.

Conclusions and relevance

Transfusion of FEA 1-negative, transfusion-naive cats with FEA 1-positive blood results in production of post-transfusion anti-FEA 1 alloantibodies as early as 5 days post-transfusion. Our results confirm the potential immunogenicity of FEA 1 and support crossmatching prior to a blood transfusion, even in transfusion-naive cats. Further studies are needed to better document the clinical importance of these post-transfusion antibodies, as well as to facilitate routine blood typing for the FEA 1 antigen in cats.

2021 ISFM Consensus Guidelines on the Collection and Administration of Blood and Blood Products in Cats

PRACTICAL RELEVANCE

Blood and blood products are increasingly available for practitioners to use in the management of haematological conditions, and can be lifesaving and therapeutically useful for patients with anaemia and/or coagulopathies. It is important for feline healthcare that donors are selected appropriately, and transfusions of blood or blood products are given to recipients that will benefit from them. Complications can occur, but can be largely avoided with careful donor management and recipient selection, understanding of blood type compatibility, and transfusion monitoring.

CLINICAL CHALLENGES

Feline blood transfusion, while potentially a lifesaving procedure, can also be detrimental to donor and recipient without precautions. Cats have naturally occurring alloantibodies to red cell antigens and severe reactions can occur with type-mismatched transfusions. Blood transfusions can also transmit infectious agents to the recipient, so donor testing is essential. Finally, donors must be in good health, and sedated as appropriate, with blood collected in a safe and sterile fashion to optimise the benefit to recipients. Transfusion reactions are possible and can be mild to severe in nature. Autologous blood transfusions and xenotransfusions may be considered in certain situations.

EVIDENCE BASE

These Guidelines have been created by a panel of authors convened by the International Society of Feline Medicine (ISFM), based on available literature. They are aimed at general practitioners to provide a practical guide to blood typing, cross-matching, and blood collection and administration.

Association of Veterinary Hematology and Transfusion Medicine (AVHTM) Transfusion Reaction Small Animal Consensus Statement (TRACS). Part 1: Definitions and clinical signs

OBJECTIVE

To use a systematic, evidence-based consensus process to develop definitions for transfusion reactions in dogs and cats.

DESIGN

Evidence evaluation of the literature was carried out for identified transfusion reaction types in dogs and cats. Reaction definitions were generated based on synthesis of human and veterinary literature. Consensus on the definitions was achieved through Delphi-style surveys. Draft recommendations were made available through industry specialty listservs and comments were incorporated.

RESULTS

Definitions with imputability criteria were developed for 14 types of transfusion reactions.

CONCLUSIONS

The evidence review and consensus process resulted in definitions that can be used to facilitate future veterinary transfusion reaction research.

Accuracy of a point-of-care major crossmatch test and risk factors for major crossmatch incompatibility in cats

Major crossmatch testing can help identify immunologic incompatibilities between blood donors and recipients; however, there are limited studies describing the accuracy of point-of-care crossmatch tests. The first aim of this study was to determine if a gel-based, point-of-care major crossmatch method (GEL-CM), without antiglobulin-enhancement, could accurately detect compatible and incompatible donor-recipient pairings, using an antiglobulin-enhanced laboratory-based major crossmatch method (LAB-CM) as the reference standard. The second aim was to describe the incidence of, and risk factors for, major crossmatch incompatibility in cats. Nineteen previously-transfused cats and 32 transfusion-naïve cats, representing 132 unique donor-recipient pairings, were included in this study. Both LAB-CM and GEL-CM tests were performed for most parings. There was poor agreement between the LAB-CM and GEL-CM results (kappa = 0.111; 95% confidence interval [CI], -0.093 to 0.314). Transfusion-naïve cats had incompatibility rates of 3% and 6% using LAB-CM and GEL-CM, respectively; previously-transfused cats had incompatibility rates of 32% and 26% using LAB-CM and GEL-CM, respectively. History of previous transfusion was the only identified cat risk factor for an incompatible LAB-CM (odds ratio [OR], 31.0; 95% CI, 3.77-254.98; P = 0.0019) and GEL-CM (OR, 5.7; 95% CI, 1.72-19.20; P = 0.0054). Further studies are needed to determine if GEL-CM can detect clinically-relevant immunologic incompatibilities that would result in transfusion reactions. Major crossmatch testing is of greater importance in cats that have previously received a transfusion.

Association of Veterinary Hematology and Transfusion Medicine (AVHTM) Transfusion Reaction Small Animal Consensus Statement (TRACS) Part 2: Prevention and monitoring

OBJECTIVE

To systematically review available evidence to develop guidelines for the prevention of transfusion reactions and monitoring of transfusion administration in dogs and cats.

DESIGN

Evidence evaluation of the literature (identified through Medline searches through Pubmed and Google Scholar searches) was carried out for identified transfusion reaction types in dogs and cats. Evidence was evaluated using PICO (Population, Intervention, Comparison, Outcome) questions generated for each reaction type. Evidence was categorized by level of evidence (LOE) and quality (Good, Fair, or Poor). Guidelines for prevention and monitoring were generated based on the synthesis of the evidence. Consensus on the final recommendations and a proposed transfusion administration monitoring form was achieved through Delphi-style surveys. Draft recommendations and the monitoring form were made available through veterinary specialty listservs and comments were incorporated.

RESULTS

Twenty-nine guidelines and a transfusion administration monitoring form were formulated from the evidence review with a high degree of consensus CONCLUSIONS: This systematic evidence evaluation process yielded recommended prevention and monitoring guidelines and a proposed transfusion administration form. However, significant knowledge gaps were identified, demonstrating the need for additional research in veterinary transfusion medicine.

Identification of 5 novel feline erythrocyte antigens based on the presence of naturally occurring alloantibodies

Background

Since the discovery of the Mik antigen, several studies have described blood incompatibilities unrelated to the AB system in cats.

Objective

To estimate the prevalence of cats with non‐AB incompatibilities associated with naturally occurring alloantibodies (NOAb), and to begin mapping the corresponding feline erythrocyte antigens (FEA).

Animals

Two hundred and fifty‐eight type A cats.

Methods

Prospectively, cats were evaluated for the presence of NOAb by crossmatching in groups of 4‐6 cats. When NOAb were detected in a cat, its plasma was used as reagent to assess for the presence of the corresponding FEA in all cats included thereafter, and agreement observed between results of this extensive blood typing was evaluated.

Results

The chance of detecting incompatibilities by randomly crossmatching 2 cats was 3.9%, which resulted in at least 7% of type A cats having NOAb. Blood typing and agreement analyses performed with 7 newly detected NOAb allowed the identification of 5 presumably distinct FEA. Feline erythrocyte antigens 1 and 5 were most frequent with prevalence of 84% and 96%, respectively. Only FEA 1‐negative status was associated with a higher risk of presenting NOAb; with 16.7% of 42 FEA 1‐negative cats having NOAb compared to 5.1% of 216 FEA 1‐positive cats.

Conclusions and Clinical Importance

This study represents a first step of FEA identification outside the AB system. Because of its prevalence and association with NOAb, FEA 1 might correspond to the Mik antigen.

Accuracy of point-of-care crossmatching methods and crossmatch incompatibility in critically ill dogs

BACKGROUND

The performance of commercial point-of-care crossmatch (CM) tests compared to laboratory tube agglutination CM is unknown. Additionally, there is limited information regarding CM incompatibility in ill dogs.

OBJECTIVES

To determine if point-of-care major CM methods are accurate in detecting compatible and incompatible tests when compared to laboratory CM methods, and to identify factors associated with CM incompatibility in dogs.

ANIMALS

Part 1 (prospective) included 63 client-owned dogs potentially requiring blood transfusion. Part 2 (retrospective) included all dogs from part 1, plus medical records of 141 dogs with major CM results.

METHODS

For part 1, major CM was performed using a tube agglutination assay (LAB-CM), a gel-based point-of-care test (GEL-CM), and an immunochromatographic point-of-care test (IC-CM). For part 2, medical record data were collected to determine rates of and risk factors for CM incompatibility.

RESULTS

Kappa agreement between the LAB-CM and GEL-CM methods could not be calculated due to a relative lack of incompatible results. Kappa agreement between the LAB-CM and IC-CM methods was 0.16 (95% confidence interval [CI] = 0-0.31, P = .007) indicating no agreement. The LAB-CM incompatibility in transfusion-naïve vs dogs that had a transfusion was 25% and 35%, (P = .3).

CONCLUSIONS AND CLINICAL IMPORTANCE

Compared to laboratory methods, point-of-care methods evaluated in our study lacked sensitivity for detecting incompatibilities. Dogs had similar rates of major CM incompatibility regardless of transfusion history. This suggests CM testing prior to transfusion be considered in all dogs however our study did not investigate clinical relevancy of incompatible LAB-CM.

Effect of dilution of canine blood samples on the specificity of saline agglutination tests for immune-mediated hemolysis

BACKGROUND

Saline agglutination tests (SATs) are widely recommended for diagnosis of immune-mediated hemolytic anemia in dogs, but there are frequent false-positive results.

OBJECTIVES

Specificity of SATs will improve at higher saline-to-blood ratios.

ANIMALS

One hundred fifty dogs treated at a veterinary referral hospital with hematocrits ≤30%.

METHODS

Prospective diagnostic accuracy study. Immune-mediated hemolysis (IMH) was considered present if a gel direct antiglobulin test (DAT) was positive and there was clinical evidence of hemolysis (n = 9), absent if another mechanism for anemia was identified and the DAT was negative or there was no hemolysis (n = 138), and if IMH status was unclear, dogs were excluded (n = 3). Saline agglutination tests were prepared at 1 : 1, 4 : 1, 9 : 1, and 49 : 1 saline-to-blood ratios, and microscopic agglutination was considered a positive result.

RESULTS

Specificity for IMH increased from 29% (95% confidence interval 20-38) at a 1 : 1 dilution to 97% (93-99) at a 49 : 1 dilution. Sensitivity was 88% (47-100) at 1 : 1 and 4 : 1 dilutions and 67% (30-93%) at 9 : 1 and 49 : 1 dilutions. Diagnostic accuracy increased from 33% (24-42) at 1 : 1 dilution to 95% (90-98) at 49 : 1 dilution.

CONCLUSIONS AND CLINICAL IMPORTANCE

If performed using a 49 : 1 saline-to-blood ratio, SATs achieve high specificity for IMH. Based on a gold standard of positive DAT and evidence of hemolysis, lower saline-to-blood ratio results should not be used because false-positive results are common.