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.