Sample Topic

Canine

Immune-Mediated Hemolytic Anemia, Canine

Summary

  • Characterized by an acute and often life-threatening anemia resulting from red cell destruction by the immune system
  • Anti-erythrocyte antibodies trigger red blood cell destruction by the immune system; red cells may be destroyed by macrophages in the spleen (extravascular hemolysis) or by complement-mediated hemolysis in the bloodstream (intravascular hemolysis)
  • Disease can be idiopathic (spontaneous) or secondary to a disease that triggers an immune response (e.g., infection)
  • Current evidence to support neoplasia, inflammatory conditions, drugs, or vaccines as a trigger for immune-mediated hemolysis is weak; however, lack of evidence does not preclude the possibility and should be considered when evaluating the individual patient
  • Associated with high morbidity and mortality; mortality rate is 30% to 70% within first 2 months after diagnosis
  • There is a high prevalence of systemic thromboembolic complications
  • There is no gold standard for the diagnosis of immune-mediated hemolytic anemia; diagnosis is based on the presence of anemia with spherocytosis, and/or agglutination of red blood cells that persists after washing, in conjunction with hyperbilirubinemia in the absence of functional hepatic disease, cholestasis, or sepsis
  • Treatment is aimed at addressing the inciting cause (if identified), suppression of the immune response, correction of anemia with transfusions as needed, prevention of thrombosis, and aggressive supportive care
  • Prognosis is guarded

Causes and Risk Factors

Causes

  • Underlying cause for the development of anti-erythrocyte antibodies is unknown; classified as idiopathic immune-mediated hemolytic anemia (IMHA)
  • A genetic component is suspected in certain dog breeds (e.g., Cocker Spaniels)
  • Infectious diseases that have been associated with the development of secondary immune-mediated hemolysis include:
  • Inflammatory conditions (e.g., pancreatitis), neoplasia, envenomation, recent vaccination, and drug therapy have all been implicated as potential triggers; however, definitive evidence is lacking

Risk Factors

  • Higher incidence in the spring and early summer; this may vary regionally

Signalment

  • Can occur in any breed; American Cocker Spaniels, Miniature Schnauzers, Collies, English Springer Spaniels, Poodles, and Bichon Frises are overrepresented
  • Young adult to middle-age dogs most often affected
  • Females are more often affected

Differential Diagnosis

  • For anemia:
  • For icterus:
    • Hepatic dysfunction
    • Biliary obstruction
    • Sepsis

Diagnosis and Screening

General Points

  • Clinical signs will vary with disease severity; onset of anemia is often severe and acute
  • There is no gold standard for the diagnosis of immune-mediated hemolytic anemia; diagnosis is based on the presence of anemia, spherocytosis and/or agglutination of red blood cells that persists after washing, in conjunction with hyperbilirubinemia in the absence of functional hepatic disease, cholestasis, or sepsis
  • Disease can be idiopathic (spontaneous) or secondary to a disease that triggers an immune response (e.g., infection, neoplasia, drug)
  • A primary cause or trigger is often not identified in dogs diagnosed with immune-mediated hemolytic anemia; however, screening for a possible inciting cause is recommended to determine the need for additional therapy/intervention

Signs and History

  • History should include questions regarding recent travel, medication administration, or vaccinations
  • Lethargy
  • Weakness
  • Anorexia
  • Tachypnea
  • Discolored urine (bilirubinurua or hemoglobinuria)
  • Vomiting, diarrhea, and polydipsia may occur less frequently
  • Dogs with concurrent thrombocytopenia may have epistaxis, melena, or petechiation

Physical Exam

  • Pale mucous membranes
  • Tachypnea
  • Tachycardia
  • Systolic heart murmur
  • Icterus
  • Splenomegaly
  • Fever
  • Hepatomegaly

Laboratory Tests

  • Routine laboratory tests
    • Complete blood count with differential
      • Moderate to marked anemia
      • Reticulocytosis; may require 3 to 5 days to develop a regenerative response
      • Spherocytosis
        • Non-immune mediated causes of spherocytosis include splenic neoplasia, envenomation, oxidative damage, and pyruvate kinase deficiency
      • Autoagglutination; confirms presence of antibodies on red cells and must be confirmed via saline agglutination test
      • Thrombocytopenia; may be due to concurrent immune-mediated platelet destruction or disseminated intravascular coagulation
      • Moderate to marked leukocytosis

    • Biochemistry panel
      • Hyperbilirubinemia
      • Elevations in alkaline phosphatase (ALP) and alanine aminotransferase (ALT)
        • May be secondary to hypoxia; however, drug-induced hepatic damage, infection, or neoplasia should be considered

    • Urinalysis
      • Bilirubinuria; suggestive of extravascular hemolysis
      • Hemoglobinuria; suggestive of intravascular hemolysis
        • Can be differentiated from hematuria by centrifugation of sample
        • Persistent discoloration of urine following centrifugation suggests hemoglobinuria

  • Saline agglutination test
    • Recommended to confirm the presence of autoagglutination
    • One drop of EDTA-anticoagulated blood is combined with 1 to 4 drops of saline on a microscope slide; evaluate for microscopic agglutination vs. rouleaux formation

  • Coombs' test (direct autoagglutination test)
    • Detects the presence of erythrocyte-bound immunoglobulin or complement
    • A positive test supports a diagnosis of immune-mediated disease; a negative result does not rule out immune-mediated disease
    • Does not provide information regarding an inciting cause (e.g., primary vs. secondary immune-mediated hemolysis)
    • This test is not required if results of the saline agglutination test are positive
    • Corticosteroids can result in a false negative result

  • Screening for babesiosis
    • Due to the high association between hemolytic anemia and babesiosis, all dogs should be screened for Babesia spp.
    • Dogs with hemolytic anemia due to babesiosis may not require immunosuppression
    • Combined testing with polymerase chain reaction (PCR) and serology is recommended
    • Repeat PCR testing is recommended for dogs who originally test negative but who have a high risk for infection based on exposure or breed

  • Screening for heartworm infection

Imaging

  • Thoracic radiography
    • Recommended for patients with evidence of respiratory disease or older patients with a suspicion for neoplasia
    • May detect interstitial lung pattern, alveolar opacities, and mild pleural effusion in patients with pulmonary thromboembolism (PTE) secondary to immune-mediated hemolysis; patients with PTE may have normal radiographs as well

  • Abdominal radiography
    • Hepatosplenomegaly is common
    • May identify other causes of hemolysis (e.g., zinc-containing foreign body)

Other Diagnostic Tests

  • Other infectious disease screening
    • Screening for other tick-borne infectious diseases is recommended, particularly for Anaplasma spp., Bartonella spp., and Ehrlichia spp.
    • Screening for Leishmania spp. should also be considered in endemic areas
    • See Causes and Risk Factors for a list of infectious diseases associated with hemolytic anemia

  • Abdominal ultrasonography
    • Can be considered in older patients with suspicion for neoplasia or concurrent illness
    • Peritoneal effusion may occur in patients with thromboembolic disease

  • Coagulation testing
    • Should be considered for patients with concurrent thrombocytopenia to evaluate for disseminated intravascular coagulation (DIC); may reveal:
      • Prolonged prothrombin time (PT)
      • Prolonged activated partial thromboplastin time (aPTT)
      • Decreased antithrombin activity
      • Increased D-dimer concentration and fibrin degradation products
      • Decreased fibrinogen concentration

  • Bone marrow aspirate and biopsy
    • Should be considered for patients with non-regenerative anemia

Treatment

General Points

  • Treatment is aimed at addressing the inciting cause (if identified), suppression of the immune response, correction of anemia with transfusions as needed, prevention of thrombosis, and aggressive supportive care to correct hydration and improve tissue perfusion
  • Withdrawal of nonessential drug therapy is recommended
  • Antibiotics are only required if there is suspicion of an underlying bacterial infection
  • Immunosuppressive therapy with glucocorticoids is recommended
    • Glucocorticoid therapy can be reduced by 25% to 50% every 2 to 4 weeks over a 3 to 6 month period once anemia is stabilized and agglutination, spherocytosis, and hyperbilirubinemia have resolved; a packed cell volume (PCV) or hematocrit should be evaluated prior to each dosage adjustment
  • The addition of second-line immunosuppressive drug should be considered for dogs with severe disease, unstable hematocrit with glucocorticoids alone, or when significant adverse effects of glucocorticoid therapy are expected
  • Antithrombotic therapy is recommended; there is no consensus on the optimal protocol
  • There is no consensus on duration of immunosuppressive therapy
    • Most dogs require treatment for 4 to 8 months
    • A minority of patients will require life-long therapy
  • Relapse of clinical disease is a common complication when tapering medications
  • There is little evidence to support splenectomy as a therapeutic option for immune-mediated hemolytic anemia
  • Referral to a veterinary internal medicine specialist or critical care specialist should be considered for patients with severe or refractory disease

Medications

  • Immunosuppressive therapy
    • Options include:

    • Prednisone 2 to 3 mg/kg PO every 24 hours, or 50 to 60 mg/m2/day for dogs > 25 kg
      • May be administered as a single dose or divided into twice daily doses
      • The initial dose can be decreased to < 2 mg/kg after the first 1 to 2 weeks of treatment if the dog is responding appropriately
    • Dexamethasone 0.2 to 0.4 mg/kg IV every 24 hours
      • Can be used initially for dogs who cannot tolerate oral medication due to vomiting

    • Azathioprine 2 mg/kg or 50 mg/m2 PO every 24 hours; long-term therapy 0.5 to 1 mg/kg PO every other day (administer glucocorticoid on the alternate days)
      • Has been associated with hepatotoxicity, bone marrow toxicity, and gastrointestinal signs

    • Cyclosporine 5 mg/kg PO every 12 hours
      • Used in conjunction with glucocorticoids in patients that have severe disease, are not responding to therapy with glucocorticoids alone or with azathioprine, or who are intolerant of high-dose glucocorticoid therapy
      • Gastrointestinal side effects, gingival hypertrophy, and nephrotoxicity have been reported
      • Immunosuppression-related infections have been reported with this agent

    • Mycophenolate 8 to 12 mg/kg PO every 12 hours
      • May cause severe vomiting and diarrhea

    • Leflunomide 2 mg/kg PO every 24 hours
      • May cause lethargy, decreased appetite, and vomiting

    • Human intravenous immunoglobulin 0.5 to 1.0 gm/kg IV over 4 to 12 hours
      • For patients refractory to other immunosuppressive therapies; considered a salvage measure
      • Allergic reactions have been reported; premedication with diphenhydramine should be considered

  • Antithrombotic therapy
    • According to the 2019 ACVIM consensus statement on the treatment of dogs with immune-mediated hemolytic anemia, anticoagulant therapy should be considered alone or in conjunction with antiplatelet therapy for all dogs except those with thrombocytopenia (platelet count < 30,000); the level of evidence to support these recommendations is weak
    • If anticoagulant therapy is not feasible due to cost or availability, antiplatelet therapy alone is recommended

      • Anticoagulant drug options
        • Unfractionated heparin 100 U/kg IV bolus, then 900 U/kg IV every 24 hours
          • Alternate dose: 150 to 300 U/kg SC every 6 hours

        • Low molecular weight heparin
          • Dalteparin 150 to 175 U/kg SC every 8 hours
          • Enoxaparin 0.8 to 1.0 mg/kg SC every 6 to 8 hours
          • A target anti-Xa assay evaluated 2 to 4 hours after dose can be considered; target range is 0.5 to 1.0 U/mL
          • If anti-Xa assay is not available, an activated clotting time or activated partial thromboplastin time can be considered

        • Direct factor Xa inhibitors
          • Rivaroxaban 1 to 2 mg/kg PO every 24 hours

      • Antiplatelet drug options
        • Clopidogrel 1 to 4 mg/kg PO every 24 hours
          • An oral loading dose of 2 to 4 mg/kg may be considered, followed by 1 to 2 mg/kg PO every 24 hours
          • An oral loading dose of 10 mg/kg on the first day of treatment can be considered in some cases

        • Aspirin 1 to 2 mg/kg PO every 24 hours
          • The optimal dose at which platelet function is reliably inhibited is unclear
          • Can be combined with clopidogrel
          • Increased risk of gastrointestinal toxicity in patients also receiving high-dose glucocorticoid therapy

Other Therapies

  • Transfusion therapy
    • Blood transfusion is often required; no association with worsening of hemolysis or alloimmunization
    • Blood typing and cross-matching should be considered for all patients undergoing transfusion therapy; persistent autoagglutination may hamper interpretation of blood typing and cross-matching
    • See Transfusion Therapy for more details

  • Supportive care
    • Intravenous fluid therapy to maintain hydration and perfusion
    • Fluid therapy should be given to optimize perfusion; a decrease in the packed cell volume (PCV) may occur, but red cell mass is unchanged

Follow-up

  • Glucocorticoid therapy can be reduced by 25% to 50% every 2 to 4 weeks over a 3 to 6 month period once anemia is stabilized and agglutination, spherocytosis, and hyperbilirubinemia have resolved; a packed cell volume (PCV) or hematocrit should be evaluated prior to each dosage adjustment
  • There is no consensus on duration of immunosuppressive therapy; most dogs require treatment for 4 to 8 months
  • Tapering of other immunosuppressive agents should begin after glucocorticoid reduction
  • A complete blood count (CBC) and biochemistry panel should be evaluated every 2 weeks during the first 2 months of therapy for dogs receiving azathioprine; every 1 to 2 months thereafter
  • A biochemistry panel should be evaluated every 2 to 3 months for dogs receiving cyclosporine
  • A CBC should be considered every 2 to 3 weeks for the first month of therapy for dogs receiving mycophenolate; every 2 to 3 months thereafter
  • Therapeutic drug monitoring can be considered for dogs that are not responding well to therapy, have relapsed, or when adverse effects of immunosuppressive therapy are suspected; evidence for appropriate pharmacokinetic targets is lacking

Prognosis

  • Prognosis is guarded; some studies (Level 3) have reported an association between hyperbilirubinemia, thrombocytopenia, and leukocytosis and a poor prognosis
  • Patients with intravascular hemolysis have a worse prognosis

Evidence

Guidelines and Consensus Statements

  • Swann JW, Garden OA, Fellman CL, et al. ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs. J Vet Intern Med. 2019 Mar 7. doi: 10.1111/jvim.15463. [Epub ahead of print]. Level B Article
  • Garden OA, Kidd L, Mexas AM, et al. ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats. J Vet Intern Med. 2019 Mar;33(2):313-34. Level B Article
  • Goggs R, Blais MC, Brainard BM, et al. American College of Veterinary Emergency and Critical Care (ACVECC) consensus on the rational use of antithrombotics in veterinary critical care (CURATIVE) guidelines: Small animal. J Vet Emerg Crit Care (San Antonio). 2019 Mar;29(2):121-31. Level B Article

Systematic Reviews/Meta-analyses

  • Swann JW, Skelly BJ. Systematic review of prognostic factors for mortality in dogs with immune-mediated hemolytic anemia. J Vet Intern Med. 2015 Jan;29(1):7-13. Level 2 Article
  • Swann JW, Skelly BJ. Systematic review of evidence relating to the treatment of immune-mediated hemolytic anemia in dogs. J Vet Intern Med. 2013 Jan-Feb;27(1):1-9. Level 2 Article

Randomized, Controlled Trials (RCTs)

  • Whelan MF, O’Toole TE, Chan DL, et al. Use of human immunoglobulin in addition to glucocorticoids for the initial treatment of dogs with immune-mediated hemolytic anemia. J Vet Emerg Crit Care (San Antonio). 2009 Apr;19(2):158-64. Level 2 Abstract

Other Studies or Reviews

  • Wells R, Guth A, Lappin M, et al. Anti-endothelial cell antibodies in dogs with immune-mediated hemolytic anemia and other diseases associated with high risk of thromboembolism. J Vet Intern Med. 2009 Mar-Apr;23(2):295-300. Level 2 Abstract
  • Duval D, Giger U. Vaccine-associated immune-mediated hemolytic anemia in the dog. J Vet Intern Med. 1996 Sep-Oct;10(5):290-5. Level 2 Abstract

  • Plumb’s Veterinary Drugs (online database), Tulsa, OK: Brief Media; 2019. Accessed April 1, 2019. Level 3
  • Piek C. Immune-mediated hemolytic anemias and other regenerative anemias. In: Ettinger SJ, Feldman EC, Cote E, ed.’s. Textbook of Veterinary Internal Medicine. 8th ed. St. Louis: Saunders Elsevier; 2017:829-37. Level 3
  • Papich MG. Saunders Handbook of Veterinary Drugs: Small and Large Animal, 4th Edition. St Louis, MO: Elsevier; 2016. Level 3
  • Hackner SG. Pulmonary thromboembolism. In: Bonagura JD, Twedt D, ed's. Kirk's Current Veterinary Therapy XV. Philadelphia: Elsevier Saunders;2014:705-10. Level 3
  • Johnson V, Dow S. Management of immune-mediated hemolytic anemia in dogs. In: Bonagura JD, Twedt D, ed's. Kirk's Current Veterinary Therapy XV. Philadelphia: Elsevier Saunders;2014:275-9. Level 3
  • Kidd L, Mackman N. Prothrombotic mechanisms and anticoagulant therapy in dogs with immune-mediated hemolytic anemia. J Vet Emerg Crit Care (San Antonio). 2013 Jan-Feb;23(1):3-13. Level 3
  • Wang A, Smith JR, Creevy KE. Treatment of canine idiopathic immune-mediated haemolytic anaemia with mycophenolate mofetil and glucocorticoids: 30 cases (2007 to 2011). J Small Anim Pract. 2013 Aug;54(8):399-404. Level 3
  • Mellett AM, Nakamura RK, Bianco D. A prospective study of clopidogrel therapy in dogs with primary immune-mediated hemolytic anemia. J Vet Intern Med. 2011 Jan-Feb;25(1):71-5. Level 3
  • Piek CJ, van Spil WE, Juius G, et al. Lack of evidence of a beneficial effect of azathioprine in dogs treated with prednisolone for idiopathic immune-mediated hemolytic anemia: a retrospective cohort study. BMC Vet Res. 2011 Apr 13;7:15. Level 3
  • Scott KC, Hansen BD, DeFrancesco TC. Coagulation effects of low molecular weight heparin compared with heparin in dogs considered to be at risk for clinically significant venous thrombosis. J Vet Emerg Crit Care (San Antonio). 2009 Feb;19(1):74-80. Level 3
  • Morley P, Mathes M, Guth A, et al. Anti-erythrocyte antibodies and disease associations in anemic and nonanemic dogs. J Vet Intern Med. 2008 Jul-Aug;22(4):886-92. Level 3
  • Piek CJ, Junius G, Dekker A, et al. Idiopathic immune-mediated hemolytic anemia: treatment outcome and prognostic factors in 149 dogs. J Vet Intern Med. 2008 Mar-Apr;22(2):366-73. Level 3
  • Weinkle TK, Center SA, Randolph JF, et al. Evaluation of prognostic factors, survival rates, and treatment protocols for immune-mediated hemolytic anemia in dogs: 151 cases (1993-2002). J Am Vet Med Assoc. 2005 Jun 1;226(11):1869-80. Level 3

Additional Reading

  • Moon A, Veir J. Vaccination and associated adverse events in dogs previously treated for primary immune-mediated hemolytic anemia. J Am Anim Hosp Assoc. 2019 Jan/Feb;55(1):29-34.
  • Zoia A, Gerou-Ferriani M, Drigo M, et al. Case-control study of plasma mean platelet component concentration and survival analysis for dogs with immune-mediated hemolytic anemia. J Am Vet Med Assoc. 2018 Jun 1;252(11):1384-92.
  • Cuq R, Blois SL, Mathews KA. Anti-thymocyte serum as part of an immunosuppressive regimen in treating haematological immune-mediated diseases in dogs. J Small Anim Pract. 2017 Jun;58(6):348-354. doi: 10.1111/jsap.12666. Epub 2017 Mar 28.
  • Morassi A, Bianco D, Park E, et al. Evaluation of the safety and tolerability of rivaroxaban in dogs with presumed primary immune-mediated hemolytic anemia. J Vet Emerg Crit Care (San Antonio). 2016 Jul;26(4):488-94.
  • Goggs R, Dennis SG, Di Bella A, et al. Predicting outcome in dogs with primary immune-mediated hemolytic anemia: results of a multicenter case registry. J Vet Intern Med. 2015 Nov-Dec;29(6):1603-10.
  • Panek CM, Nakamura RK, Bianco D. Use of enoxaparin in dogs with primary immune-mediated hemolytic anemia: 21 cases. J Vet Emerg Crit Care (San Antonio). 2015 Mar-Apr;25(2):273-7.