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Ambulance smartphone tool for field triage of ruptured aortic aneurysms (FILTR): study protocol for a prospective observational validation of diagnostic accuracy
  1. Thomas L Lewis1,
  2. Rachael T Fothergill2,
  3. Aneurysm-FILTR Study Group,
  4. Alan Karthikesalingam1,3
    1. 1St George's Vascular Institute, St George's University of London, London, UK
    2. 2Clinical Audit & Research Unit, London Ambulance Service NHS Trust, 8-20 Pocock Street, London, UK
    3. 3Cardiovascular and Cell Sciences Institute, St George's University of London, London, UK
    1. Correspondence to Alan Karthikesalingam; alankarthi{at}


    Introduction Rupture of an abdominal aortic aneurysm (rAAA) carries a considerable mortality rate and is often fatal. rAAA can be treated through open or endovascular surgical intervention and it is possible that more rapid access to definitive intervention might be a key aspect of improving mortality for rAAA. Diagnosis is not always straightforward with up to 42% of rAAA initially misdiagnosed, introducing potentially harmful delay. There is a need for an effective clinical decision support tool for accurate prehospital diagnosis and triage to enable transfer to an appropriate centre.

    Methods and analysis Prospective multicentre observational study assessing the diagnostic accuracy of a prehospital smartphone triage tool for detection of rAAA. The study will be conducted across London in conjunction with London Ambulance Service (LAS). A logistic score predicting the risk of rAAA by assessing ten key parameters was developed and retrospectively validated through logistic regression analysis of ambulance records and Hospital Episode Statistics data for 2200 patients from 2005 to 2010. The triage tool is integrated into a secure mobile app for major smartphone platforms. Key parameters collected from the app will be retrospectively matched with final hospital discharge diagnosis for each patient encounter. The primary outcome is to assess the sensitivity, specificity and positive predictive value of the rAAA triage tool logistic score in prospective use as a mob app for prehospital ambulance clinicians. Data collection started in November 2014 and the study will recruit a minimum of 1150 non-consecutive patients over a time period of 2 years.

    Ethics and dissemination Full ethical approval has been gained for this study. The results of this study will be disseminated in peer-reviewed publications, and international/national presentations.

    Trial registration number CPMS 16459; pre-results.

    • smartphone
    • mobile app
    • pre-hospital
    • ruptured abdominal aortic aneurysm

    This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See:

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    • Collaborators Aneurysm-FILTR Study Group consists of Rebecca Zipfel, Bilal Azhar, Sandeep Bahia, Edward Bayly, Joanna Bennett, Anne Cheetham, Michael Damiani, Kiran Dhaliwal, Christopher Fenner, Jordan Gillard, Laurie Glancy, Gavin Goodhart, Lara Hammond, Tony Harrington, Rob Hinchliffe, Peter Holt, Cian Hughes, Gnananandan Janakan, Heather Jarman, Harry King, Ian MacDonald, Laura Mannes, Sheraz Marker William Maynard, Heloise Mongue-Din, Fiona Moore, Mark Nash, Dare Oladokun, Jasmine Palmer, Ryan Parry, Kiran Patel, Shaneel Patel, Benjamin Patterson, Stephen Phillips, Jan Poloniecki, Mahim Qureshi, Lucy Rankin, Adam Smith, James Speak, Matt Thompson, Alberto Vidal-Diez, Mark Whitbread and Mark White.

    • Contributors AK and the FILTR study group conceived and derived the design of the study. All members of the FILTR study group provided input into creating the protocol. TLL drafted the manuscript. All authors read and approved the final manuscript.

    • Funding The study is supported by an Academy of Medical Sciences Clinical Lecturer Starter Grant awarded to author AK. It is also supported by grants from the Laerdal Foundation for Acute Medicine and South West London Academic Health and Social Care System.

    • Competing interests None declared.

    • Ethics approval Full ethical approval has been gained from the NRES Committee North West, reference 14/NW/0123. Further consultation and approval has been obtained from the NHS Health Research Authority Confidentiality Advisory Group, reference: 15/CAG/0152.

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

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