Reconstruction of pseudonymized patient-trajectories in Austria’s stroke cohort using medical record-linkage of in-patient routine documentation to establish a nation-wide acute stroke cohort of 102,107 pseudonymized patients between 2015 and 2019

Abstract

Introduction: Administrative health data are increasingly used for disease surveillance, quality assurance and research purposes. In Austria, reporting of a standardized dataset is mandatory for each patient. Patients and methods: Routine documentation includes administrative and medical data, including admission and discharge characteristics, disease-diagnosis using ICD-10, medical procedure codes, and coding of involved hospital departments. Since 2015, a three-step pseudonymization on these data is provided including a pseudonym using secure hash algorithm 256, a non-recalculable record-ID, and age-groups of 5 years, allowing the reconstruction of individual patient-trajectories. We included persons aged ⩾20 years with an in-patient treatment in Austrian hospitals for acute stroke or transient ischemic attack (TIA) between 01.01.2015 and 31.12.2019 using medical record-linkage. Results: This totals 102,107 patients (49.3% women) with 107,055 treatment episodes. An ischemic stroke (IS) occurred in 60.9% ( n = 65,133), 27.1% ( n = 29,019) had a TIA, 3.3% ( n = 3488) a subarachnoid hemorrhage, and 8.8% ( n = 9415) an intracerebral hemorrhage (ICH). The study period covers 35.2 million person-years at risk, with a hospitalization rate for acute stroke of 221.8 per 100,000 person-years (95% CI 220.2–223.3), and 185.1 per 100,000 person-years (95% CI 183.7–186.5) for IS. Unscheduled re-admissions within 1 year occurred in 29.2% (95% CI 28.8–29.7) after IS, and 41.7% (95% CI 40.0–43.3) after ICH. Recurrent stroke occurred in 5.3% (95% CI 5.1–5.5) after IS, and 5.6% (95% CI 4.9–6.4) after ICH. Discussion: We present herein the details of a novel methodology to establish a nation-wide unselected Austrian stroke cohort, and to reconstruct pseudonymized individual longitudinal patient-trajectories on a national level. This approach shows potential applications in epidemiological research, quality assessment and outcome measurement. Conclusion: This novel approach opens new research fields, facilitates international comparison, and is needed for national benchmarking to assess the achievement of goals according to the Stroke Action Plan for Europe and augment the quality of Austria’s integrated stroke care.

Hospitalization rates, stroke unit care, and recurrence rates in Austria’s stroke cohort Epidemiologic analysis of 102,107 patients in a nation-wide acute stroke cohort between 2015 and 2019

“…In our cohort, the risk of recurrent stroke after an IS was 5.3% and IS recurrences occurred in 5.0% after an IS over the investigated period, 5 with a significant 19% relative risk reduction for stroke recurrences, and 21% relative risk reduction for IS recurrences between 2015 and 2018. Declining trends of recurrence after stroke have been shown in a meta-analysis including study periods from 1961 to 2006.…”

“…Herein we present key epidemiologic data and their short-term changes for stroke care of an unselected nation-wide Austrian stroke cohort using novel medical record-linkage of Austrian in-patient routine documentation. 5…”

“…Hospitalization rates in Austria are similar to age-adjusted cumulative yearly incidence-rates of stroke in different European countries and regions as detailed in the accompanied methodology paper. 5 Feigin et al showed a divergent trend in stroke incidences between high- and low- to middle-income countries from 1970 to 2008. In high-income countries, a 42% decrease of stroke incidence was noted over the past four decades.…”

“…Details of the novel methodological approach as well as details on data sources are published separately. 5 We use pseudonymized health-related patient data from a standardized national dataset between 2015 to 2019, to establish an unselected Austrian stroke cohort. In brief, acute stroke subtype or transient ischemic attack (TIA) was classified according to the primary ICD-10 discharge diagnosis to TIA (G45), ischemic stroke (IS, I63), intracerebral (I61) or spontaneous subarachnoid hemorrhage (I60).…”

“…I64 was not used in Austria after 2013. 5 Characteristics on hospitalizations included the date of admission and discharge as well as the cause of hospital admission (i.e. primary diagnosis), medical procedure codes (e.g.…”