Cardiorespiratory Optimisation By Arteriovenous fistula ligation after transplantation – the COBALT feasibility trial.

Chief investigator: Mr Gavin Pettigrew
Primary sponsor: Cambridge University Hospitals NHS Foundation Trust and the University of Cambridge
Funder: NIHR Research, Addenbrooke’s Kidney Patient Association (AKPA), and Cambridge University Hospitals NHS Foundation Trust


Should we disconnect haemodialysis fistulas in patients after they have been transplanted successfully: the COBALT feasibility study (Cardiorespiratory Optimisation By AVF Ligation after Transplantation).

Study hypothesis

Objectives of this study:

  • To conduct a feasibility study involving six centres that mirrors a proposed Randomised Controlled Trial (RCT)*, but that uses pre-defined cut-offs with regards to patient recruitment and retention rates to justify progression to the RCT.
  • To understand patients’ and healthcare professionals’ perceived acceptability of the proposed trial design and processes, with a view to planning strategies to optimise recruitment and retention for the main RCT.
  • To assess feasibility and acceptability of a Cardiopulmonary exercise test (CPET) in the kidney transplant population, as judged by the proportion of participants who successfully complete both tests.
  • To assess patient compliance with wearing a wrist accelerometer (activity sensor).


*Proposed RCT hypothesis: In stable renal transplant patients, fistula disconnection improves cardiorespiratory fitness, thereby increasing patients’ activity levels and improving quality of life.

Study design

A randomised, open-labelled, interventional feasibility study of a proposed multicentre randomised controlled trial. 

Study contact

Name: Anna Sidders