Prognostic Factors for Mortality and Thromboembolism in Canine Immune‐Mediated Hemolytic Anemia: A Retrospective Study of 72 Dogs

Abstract

Medical records of 72 dogs diagnosed with immune-mediated hemolytic anemia (IMHA) were reviewed to find risk factors for the disease, for mortality, and for thromboembolism. Coagulation data of 32 patients were evaluated for mortality or thromboembolism risk factors. Cocker Spaniels were at increased risk for IMHA (P ϭ .012). Timing of vaccination was not associated with development of IMHA. PCV ranged from 5 to 33%, with a mean of 16 Ϯ 5%. Autoagglutination was present in 42% of the dogs. Platelet counts (n ϭ 60) varied from 3,000 to 793,000/L (mean, 160,117 Ϯ 133,571; median, 144,000). Thrombocytopenia (platelet count, Ͻ200,000/L) was present in 70% of the dogs, with severe thrombocytopenia (platelet count, Ͻ50,000/L) being present in 22%. One-step prothrombin time (OSPT) was prolonged in 28% of the dogs tested, and activated partial thromboplastin time (APTT) was prolonged in 47% of the dogs tested. Fibrin(ogen) degradation products (FDPs) were detected in 16 of 28 dogs tested (57%). Disseminated intravascular coagulation (DIC) was diagnosed in 10 of 31 (32%) dogs and was suspected in 8 dogs. Thromboemboli were found in 20 of 25 dogs given postmortem examinations. Mortality rate was 58%. Thrombocytopenia (P ϭ .008) and serum bilirubin concentration of Ͼ5 mg/dL (P ϭ .015) were risk factors for mortality, and hypoalbuminemia approached significance (P ϭ .053). Severe thrombocytopenia (P ϭ .046), serum bilirubin concentration of Ͼ5 mg/dL (P ϭ .038), and hypoalbuminemia (P ϭ .016) were risk factors for thromboembolism. On evaluation of continuous data, decreased platelet count (P ϭ .057), increased bilirubin (P ϭ .062), and decreased albumin (P ϭ .054) approached significance for decreased survival. A higher risk for thrombosis was found with increased alkaline phosphatase (ALKP) (P ϭ .042), increased bilirubin (P ϭ .047), and decreased albumin (P ϭ .012).Key words: Disseminated intravascular coagulation; Hypoalbuminemia; Icterus; Thrombocytopenia; Vaccination. Diagnosis of immune-mediated hemolytic anemia (IMHA) is based on identifying the combination of immune-mediated red blood cell (RBC) targeting (spherocytes, autoagglutination, and positive direct Coombs' test) with anemia and signs of hemolysis (hyperbilirubinemia, bilirubinuria, hemoglobinemia, or hemoglobinuria). IMHA can occur secondary to a variety of conditions, including systemic lupus erythematosus, neoplasia, and blood parasites, as well as administration of certain drugs. The majority of patients are considered idiopathic.IMHA continues to be a therapeutic challenge in small animal practice. Immunoglobulin or complement coating of RBCs leads to lysis or phagocytosis. Mortality up to 70% has been reported and often is associated with thromboembolism. 1 A number of retrospective studies have attempted to identify prognostic and risk factors associated with IMHA.1-6 Gender-and breed-related increased risk for IMHA has been documented in these studies. Icterus also seems to be an important risk factor for mortality in most studies.Pulmonary thromboemb...

Venous thromboembolism related to warm autoimmune hemolytic anemia: A case–control study

“…VTE is also recognized as a major cause of death in dogs with AIHA[12,33].Post-mortem examinations in 25 dogs with AIHA showed thromboembolism in 80% of cases[33]. In this study on 72 dogs with AIHA, severe thrombocytopenia, serum bilirubin concentration of N 5 mg/dL and hypoalbuminemia were risk factors for thromboembolism.…”

Concurrent immune‐mediated haemolytic anaemia and severe thrombocytopenia in 21 dogs

“…In people, vaccination has been suggested as a trigger for the development of immune-mediated cytopenias (Chen and others 2001) and a study of dogs with imha suggested a similar relationship (Duval and Giger 1996). However, in another retrospective study of dogs with imha , vaccination was not associated with the development of the disease (Carr and others 2002). …”

“…The variables were chosen either on the basis of their significance in previous studies or on a biological basis (Klag and others 1993, McManus and others 2001, Carr and others 2002). Correlations between the dogs' treatment and period of hospitalisation and outcome were evaluated.…”

“…Thrombocytopenia of variable severity is recognised in dogs with imha (Scott-Moncrieff and others 1997, Reimer and others 1999, Weinkle and others 2005), and Carr and others (2002) reported a negative association between thrombocytopenia and survival. Reticulated platelets have been identified in a dog with putative Evans' syndrome (Michimoto and others 2004) and Jackson and Kruth (1985) described 10 dogs with suspected concurrent imha and imt among a series of 55 dogs with immune-mediated cytopenias.…”

Leptospirosis and immune‐mediated haemolytic anaemia in a dog

“…The recent vaccination may also have played a role in triggering the IMHA. The relationship between vaccination and IMHA remains unproven, with one study suggesting a temporal association between vaccination and the onset of IMHA (Duval and Giger 1996) and other studies where such an association was not found (Carr and others 2002, Weinkle and others 2005). There are few reports of IMHA developing within days of vaccination in dogs (Duval and Giger 1996) and most of the studies evaluating a possible temporal association between the two assess the four-week period following vaccination.…”