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

ACVIM consensus statement on the treatment of immune thrombocytopenia in dogs and cats

Management of immune thrombocytopenia (ITP) in dogs and cats is evolving, but there are no evidence-based guidelines to assist clinicians with treatment decisions. Likewise, the overall goals for treatment of ITP have not been established. Immunosuppressive doses of glucocorticoids are the first line treatment, but optimal treatment regimens beyond glucocorticoids remain uncertain. Additional options include secondary immunosuppressive drugs such as azathioprine, modified cyclosporine, and mycophenolate mofetil, usually selected based on clinician preference. Vincristine, human IV immunoglobulin (hIVIg), and transfusion of platelet or red blood cell-containing products are often used in more severe cases. Splenectomy and thrombopoietin receptor agonists are usually reserved for refractory cases, but when and in which patient these modalities should be employed is under debate. To develop evidence-based guidelines for individualized treatment of ITP patients, we asked 20 Population Intervention Comparison Outcome (PICO) format questions. These were addressed by 17 evidence evaluators using a literature pool of 288 articles identified by a structured search strategy. Evidence evaluators, using panel-designed templates and data extraction tools, summarized evidence and created guideline recommendations. These were integrated by treatment domain chairs and then refined by iterative Delphi survey review to reach consensus on the final guidelines. In addition, 19 non-PICO questions covering scenarios in which evidence was lacking or of low quality were answered by expert opinion using iterative Delphi surveys with panelist integration and refinement. Commentary was solicited from multiple relevant professional organizations before finalizing the consensus. The rigorous consensus process identified few comparative treatment studies, highlighting many areas of ITP treatment requiring additional studies. This statement is a companion manuscript to the ACVIM Consensus Statement on the Diagnosis of Immune Thrombocytopenia in Dogs and Cats.

Evaluation of post-transfusion RBC alloimmunization in dogs using a gel-column crossmatch with and without anti-canine globulin enhancement

A blood crossmatch is essential to ensure RBC compatibility for previously transfused dogs. There is no gold standard crossmatch method for dogs, although the standards used most commonly by academic institutions and reference laboratories are the tube and gel-column crossmatches. Addition of anti-canine globulin (ACG) has been suggested to increase detection of RBC incompatibilities. Our objective was to determine if there is a correlation between results of a standard and an ACG-enhanced gel-column crossmatch in detecting post-transfusion RBC alloimmunization. Pre- and post-transfusion serum or plasma samples were obtained from 33 dogs for major crossmatches to 1-6 (median: 3) blood donors. Crossmatches were performed with (n = 202) and without (n = 202) ACG, with results scored by 4 observers, 3 of whom were anonymized. Ten of 33 (30%) dogs had major crossmatch incompatibilities post-transfusion. RBC incompatibilities (2-4+ agglutination) were detected only with ACG in 4 dogs, only without ACG in 3 dogs, and with both methods in 3 dogs. There was fair correlation between crossmatch methods for determination of compatibility (ρ = 0.34; p < 0.001) and incompatibility (ρ = 0.35; p < 0.001) scores. Among 4 observers, there was near-perfect agreement in determining compatibility (κ = 0.97; p < 0.001) and substantial agreement in overall scoring of incompatibility (κ = 0.77; p < 0.001). Our results suggest that detection of RBC incompatibilities in dogs can be maximized by performing a gel-column crossmatch both with and without ACG enhancement.

Effect of donor blood storage on gel column crossmatch in dogs

BACKGROUND

Compared with fresh blood, stored equine donor blood results in spurious tube crossmatch incompatibilities. Interpretation of blood crossmatch results is considered subjective.

OBJECTIVES

We aimed to determine if the duration of canine donor blood storage impacts compatibility testing using a standard gel column crossmatch and evaluate interobserver variation in the interpretation of crossmatch results.

METHODS

Observational study. Whole blood segments were obtained from 23 canine packed red blood cell (RBC) units for use in crossmatches after storage for 0, 7, 14, 21, 28, and 35 days. Major and minor crossmatches were performed using serum and RBCs, respectively, from two to three healthy "recipient" dogs per unit. All crossmatch results were interpreted by four observers, of whom three were blinded.

RESULTS

All major crossmatches (n = 61) were compatible on day 0 and remained compatible through day 35 of storage. All minor crossmatches (n = 69) were compatible at all time points, except for five donor pairs with 1 to 3+ agglutination. Repeat testing of these five donor pairs confirmed crossmatch incompatibilities on days 0 through 35, with no change in the degree of incompatibility over time. There was substantial agreement among four observers in determining compatibility (κ = 0.94) and scoring incompatibility (κ = 0.76).

CONCLUSIONS

The current practice of performing canine crossmatches with whole blood segments stored for up to 35 days is acceptable, with no spurious changes in compatibility expected over time. The substantial interobserver agreement suggests that the gel column is suitable for performing canine crossmatches in a laboratory setting with multiple personnel.

Alloimmunization in dogs after transfusion: A serial cross-match study

BACKGROUND

Cross-matching is performed to determine the serological compatibility of donor and recipient blood. Current guidelines recommend that cross-matching should be performed in dogs when an initial transfusion was performed more than 4 days ago or when the transfusion history is unknown.

HYPOTHESIS

Determination at what time point alloantibodies are detected in dogs after transfusion. The hypothesis was that dogs would form alloantibodies within 4 days after a transfusion.

ANIMALS

Twenty-one anemic dogs were transfused and monitored for at least 4 subsequent days. Exclusion criteria were persistent red blood cell (RBC) agglutination and a previous transfusion.

METHODS

Prospective observational study. Cross-matching was performed before the initial DEA 1-compatible transfusion and on days 1, 2, 3, and 4 and if possible, between day 5 and 28, using the tube method without enhancement (major cross-match, recipient controls); recipients were monitored for transfusion reactions.

RESULTS

In 12/21 dogs a positive cross-match (microscopic degree of agglutination [AD] 1+ to 2+) was observed within 4 days after the transfusion. In a nonlinear regression model, no significant association was detected between type of anemia (P = .41), RBC storage time (P = .44), immunosuppressive treatment (P = .75) nor transfusion volume (P = .70) and the occurrence of positive cross-matches within 4 days after transfusion. Another 4 dogs developed a positive cross-match (microscopic AD 1+ to 2+) after 6 to 13 days.

CONCLUSIONS AND CLINICAL IMPORTANCE

Because production of alloantibodies was detected as early as 1 day after transfusion, cross-matching should be performed before every subsequent transfusion.

Comparison of a commercial immunochromatographic strip crossmatch kit and standard laboratory crossmatch methods for blood transfusion compatibility in dogs

OBJECTIVE

To evaluate agreement between 2 standard laboratory (SL) methods and an immunochromatographic strip (ICS) method to crossmatch dogs receiving RBC transfusions. A second objective was to evaluate uninterpretable SL crossmatch results as compared to ICS in the presence of autoagglutination.

DESIGN

Prospective observational study (September 2018 to October 2019).

SETTING

University teaching hospital.

ANIMALS

Forty anemic dogs receiving RBC transfusions.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

All dogs received DEA 1-negative packed RBCs. Three crossmatch methods were evaluated against the same unit transfused to each dog: SL method performed at institutional laboratory (SL-I), SL method sent to a commercial laboratory (SL-C), and a commercially available point-of-care ICS method. Major and minor crossmatches were incompatible for 2.5%/7.5% of ICS tests, 82.5%/52.5% of SL-I tests, and 52.5%/27.5% of SL-C tests. Agreement between ICS and SL-C major (κ = 0.05) and minor (κ = 0.02) crossmatches and between ICS and SL-I major (κ = 0.009) and minor (κ = 0.03) crossmatches was slight. Agreement between SL-C and SL-I major (κ = -0.06) and minor (κ = -0.12) crossmatches was poor. Results of major and minor crossmatches were uninterpretable due to autoagglutination in 38%/38% for SL-I and 29%/18% for SL-C crossmatches. ICS method was interpretable for 93% (major) and 98% (minor) crossmatches. After exclusion of uninterpretable SL pairings, agreement still remained poor to slight between all tests. Only 1 of 40 dogs (2.5%; 95% confidence interval: <1.0%-13.2%) had an immediate immunological transfusion reaction.

CONCLUSIONS

Lack of agreement between all methodologies was noted. The high level of incompatibility predicted by SL methods despite lack of clinically relevant reactions suggests a high false incompatibility rate as compared to the ICS test. ICS testing was also able to give results more frequently in the face of autoagglutination. Further work is needed to investigate the ICS method's ability to predict clinically significant transfusion reactions.

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.