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Cancer recording in patients with and without type 2 diabetes in the Clinical Practice Research Datalink primary care data and linked hospital admission data: a cohort study
  1. Rachael Williams1,2,
  2. Tjeerd-Pieter van Staa2,
  3. Arlene M Gallagher1,2,
  4. Tarek Hammad3,4,
  5. Hubert G M Leufkens2,
  6. Frank de Vries2
  1. 1 CPRD, Medicines and Healthcare Products Regulatory Agency, London, UK
  2. 2 Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, The Netherlands
  3. 3 Office of Surveillance and Epidemiology, Food and Drug Administration, Silver Spring, Maryland, USA
  4. 4 EMD Serono Research & Development, EMD Serono, Inc, Rockland, Maine, USA
  1. Correspondence to Rachael Williams; Rachael.Williams{at}


Objectives and setting Conflicting results from studies using electronic health records to evaluate the associations between type 2 diabetes and cancer fuel concerns regarding potential biases. This study aimed to describe completeness of cancer recording in UK primary care data linked to hospital admissions records.

Design Patients aged 40+ years with insulin or oral antidiabetic prescriptions in Clinical Practice Research Datalink (CPRD) primary care without type 1 diabetes were matched by age, sex and general practitioner practice to non-diabetics. Those eligible for linkage to Hospital Episode Statistics Admitted Patient Care (HES APC), and with follow-up during April 1997–December 2006 were included.

Primary and secondary outcome measures Cancer recording and date of first record of cancer were compared. Characteristics of patients with cancer most likely to have the diagnosis recorded only in a single data source were assessed. Relative rates of cancer estimated from the two datasets were compared.

Participants 53 585 patients with type 2 diabetes matched to 47 435 patients without diabetes were included.

Results Of all cancers (excluding non-melanoma skin cancer) recorded in CPRD, 83% were recorded in HES APC. 94% of cases in HES APC were recorded in CPRD. Concordance was lower when restricted to same-site cancer records, and was negatively associated with increasing age. Relative rates for cancer were similar in both datasets.

Conclusions Good concordance in cancer recording was found between CPRD and HES APC among type 2 diabetics and matched controls. Linked data may reduce misclassification and increase case ascertainment when analysis focuses on site-specific cancers.

  • type 2 diabetes
  • cancer
  • electronic health records
  • primary care
  • hospital admissions
  • concordance

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

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  • Contributors RW, T-PvS, AG and TH designed the study. RW drafted the manuscript. RW, T-PvS, AG, TH, HGML and FdV contributed to the interpretation of the results and revision of the manuscript.

  • Funding This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests All authors confirm that they are not involved in any organisation or entity with a financial interest in or financial conflict with the subject matter or materials discussed in this manuscript. CPRD is owned by the Secretary of State of the UK Department of Health and operates within the MHRA. CPRD has received funding from the MHRA, Wellcome Trust, Medical Research Council, NIHR Health Technology Assessment programme, Innovative Medicine Initiative, UK Department of Health, Technology Strategy Board, Seventh Framework Programme EU, various universities, contract research organisations and pharmaceutical companies. The Department of Pharmacoepidemiology and Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences has received unrestricted funding for pharmacoepidemiological research from GlaxoSmithKline, Novo Nordisk, the private-public funded Top Institute Pharma (, includes cofunding from universities, government and industry), the Dutch Medicines Evaluation Board and the Dutch Ministry of Health.

  • Patient consent Not required.

  • Ethics approval Ethical approval for all purely observational research using anonymised CPRD data has been obtained from the East Midlands—Derby Research Ethics Service Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Data for this study were derived from CPRD primary care and linked data obtained under license from the UK Medicines and Healthcare products Regulatory Agency. While these data cannot be shared, in order to respect the wishes of patients who have opted out or dissented since the study was conducted, data for similar cohorts are available from CPRD subject to protocol approval and license agreements.

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