Can analyses of electronic patient records be independently and externally validated? The effect of statins on the mortality of patients with Ischaemic heart disease: a cohort study with nested case-control analysis
David Reeves, David Springate, Darren M Ashcroft, Ronan Ryan, Tim Doran, Richard Morris, Ivan Olier, Evangelos Kontopantelis(2014)
Can analyses of electronic patient records be independently and externally validated? The effect of statins on the mortality of patients with Ischaemic heart disease: a cohort study with nested case-control analysis.
BMJ Open, doi: doi:10.1136/bmjopen-2014-004952
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To conduct a fully independent and external validation of a research study based on one electronic health records database, using a different electronic database sampling the same population.
Using the Clinical Practice Research Datalink (CPRD), we replicated a published investigation into the effects of statins in patients with ischaemic heart disease (IHD) by a different research team using QResearch. We replicated the original methods and analysed all cause mortality using: (i) a cohort analysis and (ii) a case-control analysis nested within the full cohort.
Electronic health record databases containing longitudinal patient consultation data from large numbers of general practices distributed throughout the UK.
CPRD data for 34925 patients with IHD from 224 general practices, compared against previously published results from QResearch for 13,029 patients from 89 general practices. The study period was January 1996 to December 2003.
We successfully replicated the methods of the original study very closely. In cohort analysis risk of death was lower by 55% for patients on statins, compared to 53% for QResearch (adjusted HR 0.45, 95% CI 0.40 to 0.50; versus 0.47, 95% CI 0.41 to 0.53). In case-control analyses patients on statins had a 31% lower odds of death, compared to 39% for QResearch (adjusted OR 0.69, 95% CI 0.63 to 0.75; versus OR 0.61, 95% CI 0.52 to 0.72). Results were also close for individual statins.
Database differences in population characteristics and in data definitions, recording, quality and completeness had minimal impact on key statistical outputs. The results uphold the validity of research using CPRD and QResearch, by providing independent evidence that both datasets produce very similar estimates of treatment effect, leading to the same clinical and policy decisions. Together with other, non-independent, replication studies there is a nascent body of evidence for wider validity.
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- David Reeves
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