Medicine, Nursing and Allied Health Professions

INTERPRESS-IPD: The Inter-arm blood pressure difference individual patient data collaborations

Funded via the NIHR Research for Patient Benefit programme (PB-PG-0215-36009 ).


Inter-arm differences in blood pressure (IAD) are associated with increased cardiovascular and all-cause mortality in varied cohort studies. We have confirmed these associations with study level meta-analyses, however several questions remain, which such methods cannot answer, including:

  • What is the independent contribution of IAD to prognostic risk estimation for cardiovascular and all-cause mortality?
  • What minimum cut-off value for IAD defines elevated risk?
  • What is the incremental association between IAD and mortality risk?
  • Do different IAD measurement techniques affect prognostic value of IAD measurements?

 We are addressing these questions by forming an international collaboration, the ‘INTERPRESS-IPD’, to combine individual patient data (IPD) from IAD cohort studies into a single large dataset for IPD meta-analysis.

Design and method

The Collaboration will combine IPD from prospective cohorts that measured blood pressure in both arms during recruitment. Lead investigators contributing datasets will be acknowledged in all relevant publications. We will undertake a two stage meta-analysis leading to a standardised multivariable Cox regression model exploring risks of cardiovascular and all-cause mortality according to IAD.

  • The project then seeks to develop a new prognostic model for cardiovascular risk estimation that includes IAD.
  • We will explore variations in risk contribution of IAD across pre-defined subgroups, establish the lower limit of IAD that is associated with additional cardiovascular risk, and plan subgroup analysis by method of IAD measurement (sequential vs. simultaneous, and single vs. repeated measures).
  • We will perform cross-sectional analyses to describe the epidemiology of IAD in the dataset.
  • Further secondary research questions will be invited from collaborating authors.


Searches for IAD datasets are underway and unpublished datasets are sought. Scoping work has identified 12 eligible studies. Of these, 9 groups have agreed to share data. On this basis the dataset will include at least 1150 all-cause deaths and 681 cardiovascular deaths in 17153 participants.‌


This international collaboration will provide robust evidence on IAD to inform clinical care and future guidelines.

The study is registered with PROSPERO: registration number CRD42015031227.

Core Staff

Dr Chris Clark NIHR Clinical Lecturer in General Practice and Primary Care, UEMS – Principal Investigator
Prof John Campbell Professor of General Practice and Primary Care, UEMS – Principal Investigator
Kate Boddy Research Fellow, UEMS – Co-applicant
Dr Fiona Warren Medical statistician, UEMS – Co-applicant
Prof Rod Taylor NIHR Senior Investigator, UEMS – Co-applicant
Tim Eames, Medical Research Data Programmer, UEMS
Prof Victor Aboyans Head of Dept. Of Cardiology, Dupuytren University Hospital, Limoges, France – Co-applicant
Prof Lyne Cloutier Professor in Nursing at Université du Québec à Trois-Rivières, Canada – Co-applicant
Prof Richard McManus Professor of Primary Care, University of Oxford – Co-applicant
Prof Angela Shore Vice-Dean Research, UEMS – Co-applicant
Ellie Kingsland Research Administrator, UEMS

For further information please contact the Research Administrator on 01392 722821 or email



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