Objectives The validity of bullous pemphigoid and pemphigus vulgaris recording in routinely collected healthcare data in the UK is unknown. We assessed the positive predictive value (PPV) for bullous pemphigoid and pemphigus vulgaris primary care Read codes in the Clinical Practice Research Datalink (CPRD) using linked inpatient data (Hospital Episode Statistics (HES)) as the diagnostic benchmark.
Setting Adult participants with bullous pemphigoid or pemphigus vulgaris registered with HES-linked general practices in England between January 1998 and December 2017. Code-based algorithms were used to identify patients from the CPRD and extract their benchmark blistering disease diagnosis from HES.
Primary outcome measure The PPVs of Read codes for bullous pemphigoid and pemphigus vulgaris.
Results Of 2468 incident cases of bullous pemphigoid and 431 of pemphigus vulgaris, 797 (32.3%) and 85 (19.7%) patients, respectively, had a hospitalisation record for a blistering disease. The PPV for bullous pemphigoid Read codes was 93.2% (95% CI 91.3% to 94.8%). Of the bullous pemphigoid cases, 3.0% had an HES diagnosis of pemphigus vulgaris and 3.8% of another blistering disease. The PPV for pemphigus vulgaris Read codes was 58.5% (95% CI 48.0% to 68.9%). Of the pemphigus vulgaris cases, 24.7% had an HES diagnosis of bullous pemphigoid and 16.5% of another blistering disease.
Conclusions The CPRD can be used to study bullous pemphigoid, but recording of pemphigus vulgaris needs to improve in primary care.
- dermatological epidemiology
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Contributors MSMP, KEH, YV, SML, JHC, KST and SG contributed to the conception and design. MSMP, YV and SG contributed to data acquisition and analysis. MSMP, KEH, YV, SML, JHC, KST and SG contributed to the interpretation of data. MSMP drafted the manuscript and KEH, YV, SML, JHC, KST and SG critically revised the manuscript. SG is the guarantor of the work.
Funding This work was supported by the National Institute for Health Research (NIHR) Research for Patient Benefit grant (PB-PG-0817-20033). In addition, SML was supported by a Wellcome Senior Clinical Fellowship in Science (205039/Z/16/Z) grant.
Disclaimer The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care.
Patient consent for publication Not required.
Ethics approval The present study was approved by the Independent Scientific Advisory Committee for the CPRD (ISAC protocol number 18_224).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data may be obtained from a third party and are not publicly available. Data can be requested from www.cprd.com.
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