Follow-Up of Clinical Manifestations and Platelet Function Test in Patients with Essential Thrombocythemia on Anagrelide Treatment.

Introduccion: Patients with essential thrombocythemia (ET) may have abnormalities of platelet function (PF), the most frecuently are reduced response to epinephrine and ADP-induced aggregation and spontaneous aggregation. Anagrelide (A) has a phosphodiesterase inhibitor activity and may inhibit PF. Therefore, we evaluated the follow-up of clinical manifestations (CM) and the PF in a group of 42 ET patients before treatment and on hematological remission.

Materials and methods: 42 ET patients (33/9, F/M) who meet de PVSG criteria, were studied before treatment with A and on hematological remission. The CM were grouped into thrombosis (T), hemorrhages (H), microcirculation disturbances (MD) and combined (C), that included H plus MD or H plus T. Platelet function tests were perfomed with different agonists such as epinephrine, ADP, ristocetine, arachidonic acid and bovine vWF.

Results: are shown in Table I.

Abbreviations: T^≠ (4 TIAs, 1 stroke, 1 AMI), H* (1 upper gastrointestinal bleeding, 4 minor hemorrhages) C^± (1 mesenteric, portal and splenic vein thrombosis plus minor hemorrhage, 4 minor hemorrhages plus MCD), T^ψ (1 TIA, 1 stroke), H^§ (1 lower gastrointestinal bleeding) C^† (1 AIT plus minor hemorrhage).

During hematological remission spontaneous platelet aggregation disappeared in all patients except one. Abnormal epinephrine response desappeared in 16 patients, was not corrected in 10 and this abnormality appeared in 2 whose response were previously normal. Abnormal ADP response disappeared in 4 cases during treatment and this abnormality was found in 5 previously normal cases. No correlation was found between spontaneous platelet aggregation and clinical manifestations p= NS. No correlation was found between both epinephrine and ADP response and hemorrhages. No significant abnormalities were found in the response to arachidonic acid, ristocetin, and bovine vWF before or during treatment with anagrelide.

Conclusions: In this group of ET patients platelet function was not affected by the phosphodiesterase inhibibitor activity of anagrelide. Similarly bleeding manifestations were not worsen during this therapy. As previously shown spontaneous platelet aggregation desappeared in all but one patient. We have not yet an explanation for the increased microvascular disturbances during treatment.