Linking Australian Stroke Clinical Registry data with Australian government Medicare and medication dispensing claims data and the potential for bias

We aim to report the accuracy of linking data from a non‐government‐held clinical quality registry national claims and identify associated sources systematic bias. Patients with stroke or transient ischaemic attack admitted hospitals participating in Australian Stroke Clinical Registry (AuSCR) were linked Medicare medication dispensings through enrolment file (MEF). The proportion registrants datasets was calculated factors non‐merge assessed using multivariable analyses. A total 17,980 AuSCR (January 2010 – July 2014) submitted for linkage (median age 76 years; 46% female; 67% stroke); merged 97% MEF, 93% 95% dispensings. Data born Asia less likely link MEF (adjusted Odds Ratio [aOR]: 0.20; 95%Confidence Interval [CI]: 0.15, 0.27). those aged 85‐plus compared under 65 years merge (aOR 0.25; 95%CI:0.21, 0.30) but more dispensing (aOR: 2.15 (95%CI:1.71, 2.69). Linkage between AuSCR, Commonwealth achieved potential bias identified.