The Optum EHR database was current up to 30-Jun-2020.~Identification period: From 01-Apr-2007 to 30-Jun-2019~Study period: From 01-Jan-2007 to 30-Jun-2020~Index date:~First evidence of resistance to or intolerance of HU treatment in patients with PV according to modified European Leukemia Net (ELN) criteria and defined as:~HCT ≥ 45% with phlebotomy (last phlebotomy within last 3 months) Or~Platelet count > 400 x 109/L and presence of palpable splenomegaly (palpable spleen up to 3 months after platelet count)~Pre-index period:~Patients had a minimum of 3 months pre-index data available. Pre-index data availability was determined using the reported 'first month active' field.~Post-index period:~There was no minimum post-index period required. Each patient had a 'first month active' and 'last month active' reported within the database. As the 'last month active' was based on any activity in the database, including encounters such as letters and emails which occurred several months after the 'death_date' of the patient, using the 'last month active' can overestimate the follow-up for a given patient. For this reason, the end of follow-up for each patient was defined as the date of the last activity within the diagnosis, observations, prescriptions, laboratories, procedures tables or discharge date from the last visit within the visit table (whichever of these activities occurs latest). This underestimated the follow-up for some patients where they were not actively using healthcare resources.
This was an analytical and descriptive, non-interventional, retrospective cohort study of PV patients aged ≥ 18 years in the US using a secondary data source, Optum EHR database.