Prognostic factors and long-term outcome in dogs diagnosed with primary and secondary immune thrombocytopenia in Ireland.

Abstract

Objectives: The objectives of this study were to describe the outcome and prognostic factors in dogs diagnosed with primary and secondary immune thrombocytopenia (ITP).

Materials and methods: Medical records of dogs diagnosed with primary and secondary ITP in a referral hospital in Ireland were retrospectively evaluated. Short- and long-term survivals were analysed using Cox proportional-hazards regression models.

Results: Medical records from 49 dogs were included. Primary and secondary ITP were diagnosed in 81.25% and 18.75% of dogs, respectively. The survival rate was 69% at 2 weeks (95% confidence interval [CI]: 0.54 to 0.80), 63% at 3 months (95% CI: 0.48 to 0.75) and 51% at 2 years (95% CI: 0.37 to 0.65). The overall median survival time was 985 days (primary ITP only: 1084 days; secondary ITP only: 225 days). Dogs surviving 30 days post-diagnosis had a median long-term survival time of 10 years. A lower haematocrit was negatively associated with survival [hazard ratio (HR) 0.96, 95% CI: 0.92 to 0.99]. Neutrophilia (HR: 0.44, 95% CI: 0.20 to 0.96) was associated with a 66% decreased risk of death. Band neutrophilia was associated with shorter hospitalisation (regression coefficient -3.56, 95% CI: -5.70 to -1.42). Presence of petechiae and ecchymoses (regression coefficient 2.41, 95% CI: 0.41 to 4.42), and the use of a second-line immunosuppressive agent (SLI) (regression coefficient 2.11, 95% CI: 0.11 to 4.12) were significantly associated with longer hospitalisation but not with survival.

Clinical significance: A lower haematocrit was the only variable associated with a worse prognosis in dogs diagnosed with ITP. Dogs with confirmed secondary ITP had an overall shorter median survival time. Dogs surviving over 30 days had an excellent prognosis.