Management and Outcomes of Anti-thrombotic Medication Use in Thrombocytopenia

* Thrombocyte-level cohorts Patients will be divided into two groups based on the platelet level at study index . 1. Thrombocytopenic Cohort: Patients with morning platelet count below 50\*109/L at study index. This is the main study cohort for all analyses 2. Non-thrombocytopenic Cohort: Patients whose morning platelet count is ≥ 50\*109/L at study index will be considered as a reference group, and not included in the primary analysis. * Analysis of outcomes: By definition, there will be an intervention at the time of study index (baseline), meaning that even if no change is made, it will be considered an intervention. Each patient may have multiple exposures/interventions over the study. Therefore, in a time dependent analysis, each outcome will be linked to the exposure/intervention at study index. Each exposure/intervention will be linked with the platelet level on the day of the intervention. #Competing Events: The following events (in addition to death) will be considered competing events and will be considered as such in the statistical analyses of the outcomes: 1. The composite primary outcome 2. change in the antithrombotic regimen after study index 3. diagnosis of HIT or TTP 4. a change in the hematological malignancy treatment regimen. Study follow-up will continue after these events, and study data will continue to be recorded until censorship for end of study period or death. * Detecting selection bias: Patients fulfilling the inclusion criteria but not included in the study, will be detected by reviewing the medical records of the hematology institute, weekly. The baseline characteristics and reason for not including these patients will be recorded retrospectively in the "not-included cohort". The baseline characteristics of this cohort will be compared with the study cohort to ascertain whether selection bias exists.