All registered patients in CPRD practices in England
aged 12–90 years between 1 January 2000 and 31
December 2011 were included in the analysis. Any
records not classified as ‘up-to-standard’ at practice or
patient level were excluded.20 This is a measure based
on an assessment of completeness, continuity and plausibility
of data recording in key areas as regulated by the
CPRD.