Flow-mediated dilatation: learning curve study with a novice operator

Background Flow-mediated dilatation (FMD) of the brachial artery is commonly measured to assess endothelial function in experimental and clinical research studies. However, attaining reproducible results can be challenging, especially among inexperienced operators. Up to this point, no detailed learning curve study of novice operators has been published. Methods We assessed the learning curve of FMD measurement in one novice operator. Following a one-week theoretical and basic training period, the operator performed duplicate measurements on 6-8 individuals per week, over a six-week time period. During the measurements, the operator followed the recommendations of the most recent guideline on FMD measurement. Duplex ultrasound was used for the simultaneous and continuous measurement of brachial artery diameter and local blood flow velocity. Following a 1-minute recording of baseline diameter (D), FMD was measured after a 5-minute period of occlusion of the proximal forearm vessels. Inter-session coefficient of variation (CV) values of D and FMD were calculated for each week. Results The majority of participants did not have any history of cardiovascular disease. The number of volunteers assessed each week were the following: 8, 7, 7, 6, 7, 7 individuals, from week 1 to week 6. CV values for both D and FMD exhibited a decreasing trend over the training period, ending at 1.73% for D and 14.24% for FMD at week 6. The CV values at week 6 were within the range outlined in the most recent FMD guideline for proficiency. Conclusions Within a reasonable timeframe, and with careful adherence to measurement guidelines, the attainment of sound reproducibility in FMD measurements by a novice operator is feasible. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This research was supported by the NIHR Cambridge Biomedical Research Centre. The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. This research was also supported by the Evelyn Trust Grant 20/58. ### 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: Our study was performed within the confines of the "Influence of Age, Weight and Ethnic background on blood pressure: AWE study" that received favorable opinion from the West Midlands - Coventry and Warwickshire Research Ethics Committee (ethical permission number: 16/WM/0485). Verbal informed consent was received from participants. 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 All data produced in the present study are available upon reasonable request to the authors.