Immune mediated haemolytic anaemia and thrombocytopenia in 25 adult equids

Immune mediated hemolytic anemia is not uncommon in horses and can be expensive to treat when moderately severe. This reports helps us make decisions on treatment. If primary with no known comorbidity treatment is often rewarding. However in the presence of other diseases, especially cancer, or if the BUN has elevated significantly prognosis drops. The elevated BUN may be due to kidney damage from the hemolysis.
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Immune mediated haemolytic anaemia and thrombocytopenia in 25 adult equids: 1997-2016
Equine Vet J. 2020 Nov 10.
Charlotte A Easton-Jones 1 , Krista E Estell 2 , K Gary Magdesian 3
Affiliations

1 Rossdales LLP, Exning, Newmarket, Suffolk, UK.
2 Virginia Tech Marion duPont Scott Equine Medical Center – Internal Medicine, Leesburg, Virginia, USA.
3 Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA.

Abstract

Background: Information concerning clinical presentation, conditions associated with immune mediated haemolytic anaemia (IMHA) and thrombocytopenia (IMTP) and outcome in equids is lacking. Previous case reports suggest immune mediated disease and neoplasia are associated.

Objectives: Characterise the clinical presentation, clinicopathologic data, underlying conditions, treatment and outcome of IMHA and IMTP cases in equids. We hypothesise IMHA with concurrent thrombocytopenia occurs more often than IMHA or IMTP alone, that neoplasia is commonly associated with these immune diseases and cases frequently have a poor prognosis.

Study design: Retrospective case-control study.

Methods: Medical records reviewed (1997-2016). Twenty-five equids were diagnosed with IMHA, IMTP or IMHA with thrombocytopenia by Coombs test or flow cytometry. Controls were equids presented for non-immune mediated disease immediately prior to and after study animals. Fisher’s exact test was used to compare between groups for categorical variables (P<0.05). Results reported as odds ratios (OR) and 95% confidence intervals (CI). Unpaired t test and Mann Whitney test were used to compare between groups for continuous variables (P<0.05).

Results: Neoplasia incidence was significantly higher in the study population (28%) versus controls (8%) (P = 0.04). Equids with primary disease were more likely to survive to discharge than equids with secondary disease (8/9 vs. 7/16; P=0.03 OR=13.3 (95% CI: 1.3-134.7.). Survivors had a significantly lower blood urea nitrogen (BUN) than those that died or were euthanised (survivors, 6.1 ± 2.5 mmol/l vs. nonsurvivors, 9.9 ± 3.1 mmol/l P=0.003). The odds of short-term mortality were higher in horses presenting with increased BUN (OR= 19.5; 95% CI, 1.8-214.1; P= 0.009).

Main limitations: Retrospective nature of the study, small case numbers and limited long term follow up.

Conclusions: Primary IMHA/IMTP cases have a reasonable prognosis and warrant treatment. Secondary cases have a poor prognosis, and are frequently associated with cancer. BUN may have utility as a prognostic indicator for IMHA/IMTP cases.