A Phase 4, Observational Study to Explore How Different Treatment Regimens Affect Continuation With Treatment in the First 6 Months Following Initiation of XAGRID Into Adult Patients' Essential Thrombocythemia Therapy

Percentage of Subjects With Continuation of Anagrelide Hydrochloride at 6 Months: When the Dosing Was Consistent With the Summary of Product Characteristics (SmPC)

Time Frame: 6 months

Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when XAGRID treatment was initiated, using the following variables: •Initiation of XAGRID dosing consistent with the Summary of Product Characteristics (SmPC): •Consistent if: -The starting dose was \<=1 mg/day, AND -Any increase in dose was no more than 0.5mg/day, AND -Any increase in dose was made at least 7 days after first initiation or at least 7 days after any previous modification (up or down), AND -The maximum dose did not exceed 10 mg/day at any stage. •Inconsistent: in all other cases

Percentage of Subjects Achieving Platelet Target Response: Withdrawal of Previous Cytoreductive Therapy Before Anagrelide Hydrochloride Initiation

Time Frame: 6 months

Full response is a platelet count of \<400x10\^9/L. Partial response is a platelet count between 400-600x10\^9/L or a platelet count reduction of 200x10\^9. Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when Anagrelide Hydrochloride treatment was initiated, using the following variables: •Withdrawal of previous cytoreductive therapy: -Before: if a stop date of previous cytoreductive therapy was prior to the date of Anagrelide Hydrochloride initiation -After: if a stop date of previous cytoreductive therapy was between the first administration and the last administration of Anagrelide Hydrochloride during the follow-up -Not Withdrawn: in all other cases

Percentage of Subjects Achieving Platelet Target Response: When the Dosing Was Inconsistent With the Summary of Product Characteristics (SmPC)

Time Frame: 6 months

Full response is a platelet count of \<400x10\^9/L. Partial response is a platelet count between 400-600x10\^9/L or a platelet count reduction of 200x10\^9. Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when XAGRID treatment was initiated, using the following variables: •Initiation of XAGRID dosing consistent with the Summary of Product Characteristics (SmPC): •Consistent if: -The starting dose was \<=1 mg/day, AND -Any increase in dose was no more than 0.5mg/day, AND -Any increase in dose was made at least 7 days after first initiation or at least 7 days after any previous modification (up or down), AND -The maximum dose did not exceed 10 mg/day at any stage. •Inconsistent: in all other cases

Percentage of Subjects With Continuation of Anagrelide Hydrochloride at 6 Months: Withdrawal of Previous Cytoreductive Therapy Before Anagrelide Hydrochloride Initiation

Time Frame: 6 months

Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when Anagrelide Hydrochloride treatment was initiated, using the following variables: •Withdrawal of previous cytoreductive therapy: -Before: if a stop date of previous cytoreductive therapy was prior to the date of Anagrelide Hydrochloride initiation -After: if a stop date of previous cytoreductive therapy was between the first administration and the last administration of Anagrelide Hydrochloride during the follow-up -Not Withdrawn: in all other cases

Percentage of Subjects Achieving Platelet Target Response: Withdrawal of Previous Cytoreductive Therapy After Anagrelide Hydrochloride Initiation

Time Frame: 6 months

Full response is a platelet count of \<400x10\^9/L. Partial response is a platelet count between 400-600x10\^9/L or a platelet count reduction of 200x10\^9. Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when Anagrelide Hydrochloride treatment was initiated, using the following variables: •Withdrawal of previous cytoreductive therapy: -Before: if a stop date of previous cytoreductive therapy was prior to the date of Anagrelide Hydrochloride initiation -After: if a stop date of previous cytoreductive therapy was between the first administration and the last administration of Anagrelide Hydrochloride during the follow-up -Not Withdrawn: in all other cases

Percentage of Subjects Achieving Platelet Target Response: When the Dosing Was Consistent With the Summary of Product Characteristics (SmPC)

Time Frame: 6 months

Full response is a platelet count of \<400x10\^9/L. Partial response is a platelet count between 400-600x10\^9/L or a platelet count reduction of 200x10\^9. Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when XAGRID treatment was initiated, using the following variables: •Initiation of XAGRID dosing consistent with the Summary of Product Characteristics (SmPC): •Consistent if: -The starting dose was \<=1 mg/day, AND -Any increase in dose was no more than 0.5mg/day, AND -Any increase in dose was made at least 7 days after first initiation or at least 7 days after any previous modification (up or down), AND -The maximum dose did not exceed 10 mg/day at any stage. •Inconsistent: in all other cases

Percentage of Subjects With Continuation of Anagrelide Hydrochloride at 6 Months: Withdrawal of Previous Cytoreductive Therapy After Anagrelide Hydrochloride Initiation

Time Frame: 6 months

Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when Anagrelide Hydrochloride treatment was initiated, using the following variables: •Withdrawal of previous cytoreductive therapy: -Before: if a stop date of previous cytoreductive therapy was prior to the date of Anagrelide Hydrochloride initiation -After: if a stop date of previous cytoreductive therapy was between the first administration and the last administration of Anagrelide Hydrochloride during the follow-up -Not Withdrawn: in all other cases

Percentage of Subjects With Continuation of Anagrelide Hydrochloride at 6 Months: No Withdrawal of Previous Cytoreductive Therapy

Time Frame: 6 months

Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when Anagrelide Hydrochloride treatment was initiated, using the following variables: •Withdrawal of previous cytoreductive therapy: -Before: if a stop date of previous cytoreductive therapy was prior to the date of Anagrelide Hydrochloride initiation -After: if a stop date of previous cytoreductive therapy was between the first administration and the last administration of Anagrelide Hydrochloride during the follow-up -Not Withdrawn: in all other cases

Percentage of Subjects With Continuation of Anagrelide Hydrochloride at 6 Months: When the Dosing Was Inconsistent With the Summary of Product Characteristics (SmPC)

Time Frame: 6 months

Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when XAGRID treatment was initiated, using the following variables: •Initiation of XAGRID dosing consistent with the Summary of Product Characteristics (SmPC): •Consistent if: -The starting dose was \<=1 mg/day, AND -Any increase in dose was no more than 0.5mg/day, AND -Any increase in dose was made at least 7 days after first initiation or at least 7 days after any previous modification (up or down), AND -The maximum dose did not exceed 10 mg/day at any stage. •Inconsistent: in all other cases

Percentage of Subjects Achieving Platelet Target Response: No Withdrawal of Previous Cytoreductive Therapy

Time Frame: 6 months

Full response is a platelet count of \<400x10\^9/L. Partial response is a platelet count between 400-600x10\^9/L or a platelet count reduction of 200x10\^9. Patients who had taken a previous cytoreductive therapy were divided into subgroups based on the treatment regimens used when Anagrelide Hydrochloride treatment was initiated, using the following variables: •Withdrawal of previous cytoreductive therapy: -Before: if a stop date of previous cytoreductive therapy was prior to the date of Anagrelide Hydrochloride initiation -After: if a stop date of previous cytoreductive therapy was between the first administration and the last administration of Anagrelide Hydrochloride during the follow-up -Not Withdrawn: in all other cases