Reliability of single-lead electrocardiogram interpretation to detect atrial fibrillation: insights from the SAFER Feasibility Study

Background and Aims Single-lead electrocardiograms (ECGs) can be recorded using widely available devices such as smartwatches and handheld ECG recorders. Such devices have been approved for atrial fibrillation (AF) detection. However, little evidence exists on the reliability of single-lead ECG interpretation. We aimed to assess the level of agreement on detection of AF by independent cardiologists interpreting single lead ECGs, and to identify factors influencing agreement. Methods In a population-based AF screening study, adults aged ≥65 years old recorded four single-lead ECGs per day for 1-4 weeks using a handheld ECG recorder. ECGs showing potential AF were identified by a nurse with the aid of an automated algorithm. These ECGs were reviewed by two independent cardiologists who assigned participant- and ECG-level diagnoses. Inter-rater reliability of AF diagnosis was calculated using linear weighted Cohen’s kappa (𝜅𝑤). Results 185 participants and 1,843 ECGs were reviewed by both cardiologists. The level of agreement was moderate: 𝜅𝑤 = 0.42 (95% CI, 0.32 – 0.52) at the participant-level; and 𝜅𝑤 = 0.51 (0.46 – 0.56) at the ECG-level. At participant-level, agreement was associated with the number of adequate-quality ECGs recorded, with higher agreement in participants who recorded at least 67 adequate-quality ECGs. At ECG-level, agreement was associated with ECG quality and whether ECGs exhibited algorithm-identified possible AF. Conclusions Inter-rater reliability of AF diagnosis from single-lead ECGs was found to be moderate in older adults. Strategies to improve reliability might include participant and cardiologist training and designing AF detection programmes to obtain sufficient ECGs for reliable diagnoses. ### Competing Interest Statement MRC is employed by Astrazeneca PLC. BF has received speaker fees, honoraria, and non-financial support from the BMS and Pfizer Alliance; and loan devices for investigator initiated studies from Alivecor: all were unrelated to the present study, but related to screening for AF. SJG has received honoraria from Astra Zeneca and Eli Lilly for contributing to postgraduate education concerning type 2 diabetes to specialists and primary care teams. FDRH reports occasional consultancy for BMS/Pfizer, Bayer and BI over the last five years. HCL is employed by Zenicor Medical Systems AB. GYHL: Consultant and speaker for BMS/Pfizer, Boehringer Ingelheim, Daiichi-Sankyo, Anthos. No fees are received personally. JM has performed consultancy work for BMS/Pfizer and Omron. PHC has performed consultancy work for Cambridge University Technical Services, and has received honoraria from IOP Publishing and Emory University (the latter not received personally). ### Funding Statement This study is funded by the National Institute for Health Care Research (NIHR), grant number RP-PG-0217-20007; and the British Heart Foundation (BHF), grant number FS/20/20/34626. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The SAFER (Screening for Atrial Fibrillation with ECG to Reduce stroke) Feasibility Study ([ISRCTN 16939438][1]), was approved by the London-Central Research Ethics Committee (REC ref: 18/LO/2066). All participants gave written informed consent. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Requests for pseudonymised data should be directed to the SAFER study co-ordinator (Andrew Dymond using SAFER{at}medschl.cam.ac.uk) and will be considered by the investigators, in accordance with participant consent. [1]: /external-ref?link_type=ISRCTN&access_num=ISRCTN16939438