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Research article:

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

Reference:

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

Link to fulltext article
Abstract
Objective 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. Design 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. Setting Electronic health record databases containing longitudinal patient consultation data from large numbers of general practices distributed throughout the UK. Participants 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. Results 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. Conclusion 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.
Author for correspondence
David Reeves
Email for correspondence
david.reeves@manchester.ac.uk

Code list: Hypertension

24 codes in list

Code Coding system Description Entity type List name
2126100 Read Hypertension resolved diagnostic Hypertension
G2...00 Read Hypertensive disease diagnostic Hypertension
G20..00 Read Essential hypertension diagnostic Hypertension
G200.00 Read Malignant essential hypertension diagnostic Hypertension
G201.00 Read Benign essential hypertension diagnostic Hypertension
G20..11 Read High blood pressure diagnostic Hypertension
G202.00 Read Systolic hypertension diagnostic Hypertension
G203.00 Read Diastolic hypertension diagnostic Hypertension
G20z.00 Read Essential hypertension NOS diagnostic Hypertension
G20z.11 Read Hypertension NOS diagnostic Hypertension
G24..00 Read Secondary hypertension diagnostic Hypertension
G240.00 Read Secondary malignant hypertension diagnostic Hypertension
G240000 Read Secondary malignant renovascular hypertension diagnostic Hypertension
G240z00 Read Secondary malignant hypertension NOS diagnostic Hypertension
G241.00 Read Secondary benign hypertension diagnostic Hypertension
G241000 Read Secondary benign renovascular hypertension diagnostic Hypertension
G241z00 Read Secondary benign hypertension NOS diagnostic Hypertension
G244.00 Read Hypertension secondary to endocrine disorders diagnostic Hypertension
G24z.00 Read Secondary hypertension NOS diagnostic Hypertension
G24z000 Read Secondary renovascular hypertension NOS diagnostic Hypertension
G24z100 Read Hypertension secondary to drug diagnostic Hypertension
G24zz00 Read Secondary hypertension NOS diagnostic Hypertension
G2y..00 Read Other specified hypertensive disease diagnostic Hypertension
G2z..00 Read Hypertensive disease NOS diagnostic Hypertension

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