Incident VTE cases were those who had a first VTE diagnosis after 1 January 2005 and with at least 5 years of look-back period. Those with a first VTE diagnosis less than 5 years of look-period were considered as undetermined VTE cases.

Events during the 3 months before the first VTE recurrence will be described. Potential risk factors that will be evaluated include age, gender, and treatment regimen for VTE, adherence to treatment regimen, concomitant medications, and comorbidity. The analysis will be stratified by the nature of the first VTE (provoked and unprovoked). Due to the unknown number of repeated recurrence and complex clinical nature of patients with multiple VTE recurrence, risk factors for multiple recurrences will be evaluated at a less detailed level than that for the first recurrence.

All deaths before 31 December 2014 among the incident VTE patients were identified through the mortality records. Patients were followed from incident VTE index date, and the patients were censored on 31 December 2014 or termination of NHI coverage without further medical or mortality records. If the patient died during the same hospitalization during the incident VTE, the death date was defined as the discharge date of that specific hospitalization.

Major bleeding (intracranial bleed and gastrointestinal bleed) was the major morbidity of interest and incident VTE patients were followed from incident VTE index date till 31 December 2014, death or termination of NHI coverage without any further medical records. Patients died during the incident VTE hospitalization were excluded for major bleeding follow up.