A retrospective study of the treatment and follow-up of primary immune-mediated thrombocytopenia in dogs

The primary immune-mediated thrombocytopenia (Idiopathic Thrombocytopenic Purpura, ITP) is a relatively uncommon hematological disorder in dogs. So far, there are only a limited number of studies about the treatment approach, the follow-up and the survival time (1-3). This retrospective study was arranged to collect in ITP cases: treatment approaches and responses during the 1st year of follow-up; the influence of therapy and dosages set-up by external referring vets in comparison to the response to the treatment prescribed in our Veterinary Teaching Hospital (VTH) in un-treated patients; the course of the disorder, followup, relapses and the survival of patients. Twenty-five cases of ITP (May 2010 - December 2017) were included. Details about signalment, history including immunosuppressive treatments previously prescribed by external referring vets, and clinical signs were collected. The course of the disease, modification of therapy, relapses and survival at several times (days T0, T7, T14, T30, T60, T90, T180, and T365) were monitored and evaluated (Chi square or Fisher test). Patients treated previously for immune-mediated hemolytic anemia (n=5) or underwent to splenectomy (n=2) were separately evaluated. Thirteen cases arrived at the VTH previously treated: 1/13 only cyclosporine 5 mg/kg/bid, 9/13 with corticosteroids, and 3/13 with combination of corticosteroids and another immunesuppressive drug (among the corticosteroid dosages used 7/13 have been treated with immunosuppressive doses and 5/13 with anti-inflammatory doses). The duration of the corticosteroids administration, the complete immune-suppressive therapy, the incidence of relapse and survival times were not statistically different between patients previously treated and those un-treated. The speed of the platelet count increase was higher during the first 7 days of treatment using corticosteroid. Indeed, if the platelet count at T0 was lower than 20x10⁹ /L, the platelet count increases by about 44 times at T7. If the platelet count at T0 was greater than 20x10⁹ /L, the platelet count increases by only 2 times at T7. The relapse of ITPs has been seen in 40% of cases, and the dosage tapering was the main cause. Only 1/25 death at about T30 was recorded. Splenectomy resulted an appropriate therapeutic option even if with low number of cases treated. The immune-suppressive therapy with inappropriate dosages did not influence the relapse or the survival of patients. On the contrary, the time for patients to respond to the treatment was extended and therefore was increased the development of adverse effects. The speed at which the number of platelets increases was depending on the basal count. The ITP cases showed a good prognosis within the initial one year of treatment and were not been influenced by the duration of therapy, drugs used, appropriate dosages or the occurrence of relapse.