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

Preliminary Study on Treatment Outcomes and Prednisolone Tapering after Marine Lipid Extract EAB-277 Supplementation in Dogs with Immune-Mediated Hemolytic Anemia

Immune-mediated hemolytic anemia (IMHA) is a common autoimmune disorder in dogs with a high fatality rate and it remains a therapeutic challenge. The marine lipid extract, EAB-277, is a natural anti-inflammatory nutraceutical product. However, the effects of EAB-277 in IMHA dogs has rarely been investigated. The objective of this study is to assess the clinical effects of EAB-277 and prednisolone dose-tapering for supplemental therapy in IMHA dogs. Prednisolone was given to 18 anemic IMHA dogs according to a standard regimen. Six dogs were supplementally treated with EAB-277 for 28 days and the remaining twelve dogs were a control group of untreated supplementations. The results demonstrate that the supplement group showed slightly better survival rates (66.7 ± 19.2%) than the control group (16.7 ± 0.7%), but the difference was not statistically significant (p = 0.408). When compared to pre-therapy, the supplement group's blood profiles improved (p < 0.05). The EAB-277 treated group showed a moderate decrease in the incidence rate (4.20 times) of prednisolone tapering compared to the control group. The dosage reduction of prednisolone in supplement group was more than that in the control group (p < 0.0001). Our results suggest that EAB-277 supplementation may enhance clinical outcomes and lessen prednisolone dose-tapering in canine IMHA therapy.

Babesia gibsoni Infection in a Cat with Immune-Mediated Haemolytic Anaemia and Thrombocytopenia

Tick-borne haemoparasite Babesia gibsoni has been detected rarely in cats, in surveys of apparently healthy animals. In stored blood from a 6-year-old male-neutered domestic shorthair cat in Hong Kong, B. gibsoni DNA was detected retrospectively using PCR for Babesia spp. 18S rRNA and mitochondrial cytochrome B genes, followed by sequencing and basic local alignment search tool (BLAST) analysis. The cat presented with severe haemolytic anaemia and thrombocytopenia. The cat responded to supportive care and glucocorticoids and was clinically normal despite persistent subclinical thrombocytopenia until six months after presentation, when it succumbed to a fatal haemorrhagic episode. Necropsy revealed severe intestinal and pulmonary haemorrhage and hypocellular bone marrow with megakaryocytosis but no other causes of immune-mediated thrombocytopenia (IMTP) or immune-mediated haemolytic anaemia (IMHA). Blood stored on days 158 and 180 tested PCR negative for Babesia spp. This report demonstrates that geographic range of B. gibsoni detection in cats includes Hong Kong. The exclusion of other causes suggests that B. gibsoni might have potentially played a role in triggering immune-mediated disease in this case.

The Indirect Antiglobulin (Coombs') Test Is Specific but Less Sensitive Than the Direct Antiglobulin Test for Detecting Anti-Erythrocytic Autoantibodies and Thereby Immune-Mediated Hemolytic Anemia in Dogs

The immunodiagnostic assessment of dogs suspected of having immune-mediated hemolytic anemia (IMHA) is based on persistent autoagglutination of erythrocytes (after three saline washes), marked spherocytosis, and a positive direct antiglobulin (Coombs') test (DAT). However, the value of using the indirect antiglobulin test (IAT) for the detection of anti-erythrocytic autoantibodies in serum from dogs suspected of having IMHA is unclear. To evaluate the IAT, leftover serum samples from a large cohort of 94 dogs suspected of having IMHA and for which DAT results were known were incubated with DAT- erythrocytes, and five IAT techniques were performed (in part with different reagents and temperatures): microtiter plate (MICRO), microcapillary, laboratory gel column, gel minitube kit (GEL KIT), and immunochromatographic strip kit. Two IAT techniques (MICRO at 37 °C and GEL KIT with rabbit anti-dog polyvalent reagent) detected autoantibodies against erythrocytes in serum from 53% and 57% of DAT+ dogs, respectively, while other IATs performed less well. Moreover, while the analytic specificity of the IAT methods compared to the DAT ranged from 96-100%, the sensitivity range was only 9-57%. Thus, we still recommend DAT for diagnosis and monitoring of IMHA in dogs but conclude that a positive IAT result may aid diagnostically when serum is available, but fresh red blood cells are not.

Validation of a cage-side agglutination card for Dal blood typing in dogs

BACKGROUND

Although 98% of the canine population is Dal-positive, Dal-negative dogs are more common in some breeds such as Doberman Pinschers (42.4%) and Dalmatians (11.7%), and finding compatible blood for these breeds may be challenging, given limited access to Dal blood typing.

OBJECTIVES

To validate a cage-side agglutination card for Dal blood typing and determine the lowest packed cell volume (PCV threshold) at which interpretation remains accurate.

ANIMALS

One-hundred fifty dogs, including 38 blood donors, 52 Doberman Pinschers, 23 Dalmatians and 37 anemic dogs. Three additional Dal-positive canine blood donors were included to establish the PCV threshold.

METHODS

Dal blood typing was performed on blood samples preserved in ethylenediaminetetraacetic acid (EDTA) <48 hours using the cage-side agglutination card and a gel column technique (gold standard). The PCV threshold was determined using plasma-diluted blood samples. All results were read by 2 observers, blinded to each other's interpretation and to the sample's origin.

RESULTS

Interobserver agreement was 98% and 100% using the card and gel column assays, respectively. Overall, the sensitivity and specificity of the cards were 86%-87.6% and 96.6%-100%, respectively, depending on the observer. However, 18 samples were mistyped using the agglutination cards (15/18 by both observers): 1 false-positive (Doberman Pinscher), and 17 false-negative samples including 13 anemic dogs (PCV range, 5%-24%; median, 13%). The PCV threshold allowing reliable interpretation was determined to be >20%.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dal agglutination cards are reliable as a cage-side test, but results should be interpreted cautiously in severely anemic patients.

Retrospective analysis of immunosuppressive and anti-thrombotic protocols in nonassociative immune mediated hemolytic anemia in dogs

BACKGROUND

Evidence supporting the effectiveness of therapeutic protocols for nonassociative immune-mediated hemolytic anemia (na-IMHA) is weak.

HYPOTHESIS/OBJECTIVES

Investigate the efficacy of various drugs in na-IMHA.

ANIMALS

Two hundred forty-two dogs.

METHODS

Multi-institutional retrospective study (2015-2020). Immunosuppressive effectiveness was determined by time to packed cell volume (PCV) stabilization and duration of hospitalization through analysis by mixed model linear regression. Occurrence of disease relapse, death, and antithrombotic effectiveness, were analyzed using mixed model logistic regression.

RESULTS

Use of corticosteroids vs a multi-agent protocol had no effect on time to PCV stabilization (P = .55), duration of hospitalization (P = .13), or case fatality (P = .06). A higher rate of relapse (P = .04; odds ratio: 3.97; 95% confidence interval [CI]: 1.06-14.8) was detected in dogs receiving corticosteroids (11.3%) during follow-up (median: 28.5 days, range: 0-1631 days) compared to multiple agents (3.1%) during follow up (median: 47.0 days, range: 0-1992 days). When comparing drug protocols, there was no effect on time to PCV stabilization (P = .31), relapse (P = .44), or case fatality (P = .08). Duration of hospitalization was longer, by 1.8 days (95% CI: 0.39-3.28 days), for the corticosteroid with mycophenolate mofetil group (P = .01) compared to corticosteroids alone. Use of clopidogrel vs multiple agents had no effect on development of thromboses (P ≥ .36).

CONCLUSIONS AND CLINICAL IMPORTANCE

Addition of a second immunosuppressive agent did not alter immediate outcome measures but might be associated with a reduction in relapse. Use of multiple antithrombotic agents did not reduce incidence of thrombosis.

Comparative study of immunohematological tests with canine blood samples submitted for a direct antiglobulin (Coombs') test

BACKGROUND

A 2019 ACVIM consensus statement on diagnostics for immune-mediated hemolytic anemia (IMHA) in dogs made testing recommendations. As data on the performance of immunohematological tests was lacking, we undertook a comparative analysis.

MATERIAL AND METHODS

Anticoagulated blood samples from 126 dogs suspected of having IMHA submitted to a diagnostic veterinary laboratory for a routine direct antiglobulin test (DAT) and from 28 healthy control dogs were evaluated for spherocytosis and autoagglutination before and after three saline washes. Samples were also subjected to different DATs: a gel minitube and an immunochromatographic strip kit used in clinics; neutral gel column cards, microtiter plates (at 4°, 22°, and 37°C), capillary tubes, and flow cytometry used in laboratories.

RESULTS

Samples from healthy dogs yielded negative results with all immunodiagnostic tests. Among the 126 samples submitted for DAT 67 were positive by a DAT utilizing microtiter plates with goat anti-dog antiglobulin DAT at 22°C. Notably, DAT results were comparable and consistent across all evaluated methods regardless of antiglobulin and temperature used. DAT+ dogs were more severely anemic and more likely to have erythroid regeneration compared to DAT- dogs. Macroscopic agglutination in tubes or on slides was observed in 48 samples after 1:1 and 1:4 blood to saline dilution, but only persisted in four samples after washing. Among the DAT+ samples, 57% had agglutination, 87% had spherocytosis, and 45% had both. There was good correlation between spherocytosis and DAT results from the six DAT techniques, but the correlation with autoagglutination was only fair. Clinical follow-up was available for 42 dogs. Of the sample from 12 DAT+ dogs collected during treatment, 10 remained DAT+ when tested 1-24 weeks after initial assessment.

CONCLUSIONS

Based upon this comparative prospective survey, all in-clinic and laboratory DAT techniques produced similar results when performed by trained personnel and can therefore be recommended for detection of antibody-coated erythrocytes and immunohematological diagnosis. In addition, use of these tests for monitoring response of IMHA dogs to treatment might be valuable.

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.