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SURF  |   May 2019
Can Osteopathic Medical Students Accurately Measure Abdominal Aortic Dimensions Using Handheld Ultrasonography Devices in the Primary Care Setting?
Kimberly Hower, OMS IV; Clipper F. Young, PharmD, MPH, CDE, BC-ADM; Alesia Wagner, DO; Dean Thorsen, PhD, DO; Joy Dugan, DHSc, MPH, PA-C
Author Notes
  • From the Touro University California College of Osteopathic Medicine (TUCOM) in Vallejo (Student Doctor Hower); the Primary Care Department at TUCOM (Drs Young, Wagner, and Dugan); the Department of Anesthesiology at Washington University School of Medicine in St Louis, Missouri (Dr Thorsen); and the Touro University California College of Education and Health Science in Vallejo (Dr Dugan). Dr. Thorsen was a medical student at the time of the study. 
  • Financial Disclosures: None reported. 
  • Support: None reported. 
  •  *Address correspondence to Kimberly Hower, OMS IV, Touro University California College of Osteopathic Medicine, 1310 Club Dr, Vallejo, CA 94592-1187. Email: kimberly.hower@tu.edu
     
Article Information
Imaging / Medical Education / Preventive Medicine
SURF   |   May 2019
Can Osteopathic Medical Students Accurately Measure Abdominal Aortic Dimensions Using Handheld Ultrasonography Devices in the Primary Care Setting?
The Journal of the American Osteopathic Association, May 2019, Vol. 119, e19-e24. doi:https://doi.org/10.7556/jaoa.2019.056
The Journal of the American Osteopathic Association, May 2019, Vol. 119, e19-e24. doi:https://doi.org/10.7556/jaoa.2019.056
Abstract

Context: The US Preventive Services Task Force (USPSTF) recommends a 1-time ultrasonography (US) screening for abdominal aortic aneurysm (AAA) to reduce AAA-specific mortality in men aged 65 to 75 years who have ever smoked. A 2015 study concluded that less than 50% of at-risk primary care patients are screened for AAA. To increase screening rates, it would be beneficial to train other health care professionals in accurately measuring abdominal aortic dimensions.

Objective: To determine whether osteopathic medical students can use handheld US machines to measure abdominal aortic diameters as accurately as an experienced US technologist.

Methods: Three osteopathic medical students underwent 8 hours of US training with a board-certified radiologist to measure abdominal aortic dimensions using a handheld US device. After the training, students independently conducted AAA US screenings at a clinic on participants meeting USPSTF AAA screening criteria. Transverse and anteroposterior measurements were taken at 3 sites: celiac axis, inferior to the renal arteries, and superior to the iliac bifurcation. A US technologist then measured the participants’ aortic diameters in the radiology department at another facility. The measurements from both reports were then compared using a 2-sample t test.

Results: The aortic diameter was measured in 16 participants with a mean (SD) body mass index of 26.7 (3.6). The mean (SD) difference between novice and expert measurement of the abdominal aorta was −0.15 (0.23) cm. No statistically significant difference was found between the US measurements completed by students and a US technologist (t=−1.38, P=.09). None of the participants met the criteria for AAA (>3.0 cm), with the largest abdominal aorta scanned by experts measuring 2.86 cm.

Conclusion: When properly trained, osteopathic medical students can accurately measure abdominal aortic diameters using a handheld US device. Training more medical students in ultrasonography would offer increased screening opportunities and possibly reduce AAA-related mortality. Further studies are needed to assess the ability of osteopathic medical students to accurately measure AAAs, as no participants in this study met the criteria for AAA.

The United States Preventive Services Task Force (USPSTF) recommends a 1-time ultrasonography (US) screening for an abdominal aortic aneurysm (AAA) in men aged 65 to 75 years who have ever smoked.1 The Grade B recommendation by the USPSTF found moderate evidence that screening for AAA in this population would potentially lead to decreased AAA-specific mortality through surgical repair of large AAAs (≥5.5 cm) and conservative management with repeated US for smaller AAAs (3.0-5.4 cm).1 The prevalence of AAA in this population is 6% to 7%, making it especially important to screen men who have ever smoked. Once an AAA ruptures, the mortality rate can be as high as 90%; therefore, increasing AAA screening opportunities can potentially decrease associated mortality. 
There is good evidence that abdominal US performed in a setting with a credentialed technologist is an accurate screening test for AAA.3 Asymptomatic AAA screening has been performed in emergency departments, cardiology offices, hospitals, and primary care offices with handheld US devices.4-7 Studies have demonstrated that medical students can successfully measure the abdominal aortic diameter.4,8-10 In one study, hospitalized patients in France were screened for AAA by medical students using handheld US devices.4 When compared with a radiologist, the correlation coefficients between 4 sets of aortic measurement were all greater than 0.91, with the mean difference between the measurements less than 1 mm.4 
Another study conducted at a vascular diagnostic laboratory in the United Kingdom evaluated the effectiveness of US AAA screening by a medical student, a newly employed vascular technologist, and a physical education graduate following a 15-day training program.8 These 3 novices were able to measure the maximal coronal diameter for AAA screening within a range of 0.46 cm to 0.52 cm of the true diameter.8 To our knowledge, no studies have evaluated US aortic measurement by osteopathic medical students. 
The USPSTF examined 4 large trials and found that a 1-time US screening for AAA is associated with reduced AAA-specific mortality.1 Also, a 2010 meta-analysis validated population-based AAA screening in men older than 65 years, with a long-term, 10-year reduction of AAA-related mortality by 45%.11 The USPSTF also showed a risk reduction in AAA rupture and emergency surgery that persisted up to 10 and 13 years, respectively. The risk of rupture varies by the size of the aneurysm. Aneurysms between 3.0 and 3.9 cm in diameter have an annual risk for rupture of 0%, those between 4.0 and 4.9 cm have a 1% annual risk for rupture, and those between 5.00 and 5.99 cm have an 11% annual risk for rupture.1,12 Many patients who presented with ruptured AAA were not previously screened, especially those in areas with limited access to diagnostic procedures or radiology services. The USPSTF estimates that less than 50% of at-risk patients were screened using US.1 
The objective of this pilot study was to determine whether osteopathic medical students can accurately measure normal abdominal aortas in a family medicine clinic with limited US training and yield results consistent with the experienced US technologist in outpatient facilities. We hypothesized that osteopathic medical students could reliably measure the abdominal aortic diameter with handheld US devices in a family medicine clinic. 
Methods
This prospective pilot study was conducted between February 2016 and July 2016, and it was approved by both the Touro University California Institutional Review Board and the Solano County Family Health Services Research Committee. Qualifying participants who met USPSTF AAA screening criteria at the Solano County Family Health Services Clinic affiliated with Touro University California in Vallejo were enrolled. The screening criteria included adult male patients aged between 65 and 75 years with any history of smoking. Potential participants were identified by (1) a daily list of patients presenting to the clinic for care to be recruited directly in the office and (2) a search of participating physicians’ patient medical records for patients matching study criteria to be recruited by phone. 
At the time of the in-office screening, the details of the study were explained to potential participants. Time was allotted to review the risks and benefits and to answer all questions, and signed informed consent was obtained. Participants were given a questionnaire to assess their cardiovascular risk for AAA. The questionnaire included the following: gender, age, smoking history, consent to partake in the study, and agreement to follow up with a hospital or outpatient US technologist within 60 days. Each participant was assigned a numerical code for identification purposes. 
Three osteopathic medical students underwent 8 hours of US training with a board-certified radiologist to learn how to measure abdominal aortic diameters using a handheld US device (Vscan Pocket Ultrasound, General Electric Company). The US training included online PowerPoint (Microsoft Corporation) lectures, US simulations, hands-on US experience, and a quantitative assessment to demonstrate competency. All investigators were required to complete a written and practical competency assessment evaluated by the staff radiologist. After the training, students independently performed US on participants who met the USPSTF AAA screening criteria. Using the handheld US device, the students evaluated maximal diameters of the abdominal aorta according to the American College of Radiology, American Institute of Ultrasound in Medicine, and the Society of Radiologists in Ultrasound Practice Parameter for the Performance of Diagnostic and Screening Ultrasound of the Abdominal Aorta in Adults.2 
Measurements were obtained in the anteroposterior and transverse dimensions at 3 sites: celiac axis, just distal to the renal arteries, and just above the iliac bifurcation.2 Means (SDs) for these 3 sites were determined and used for analysis. If an aneurysm (diameter ≥3.0 cm) was identified during aortic measurements, the image quality was reassessed to ensure that the aneurysm was completely captured in the image. If any emergent conditions were identified, the principal investigator would be alerted and the patient would be referred to the appropriate emergency services. All aortic measurements greater than 5.5 cm would be referred to vascular surgery.17 
All digital images were stored in the US device and reviewed by a principle investigator (A.W. or J.D.) for adequacy of examination and appropriateness of the measurement. The participants’ body mass index was also recorded. Each participant was screened for AAA by 1 of 3 students (including K.H. and D.T). In-office US results were neither shared with the participant nor the US technologist. Participants were then referred to an outside facility, Sutter Solano Radiology Department in Vallejo, to be screened by a US technologist. Appointments occurred within 60 days of the student US evaluations. Each operator (the student and the technologist) was blinded to each other's results. After the US images were taken by the technologist, the radiologist reviewed them and culculated the aortic measurements. The measurements from both reports were then compared using a t test. Physicians of study participants obtained copies of the outside US reports, and the participants were treated according to the USPSTF guidelines by their physicians. 
Results
During the AAA screening period, osteopathic medical students scanned 28 male smokers aged between 65 and 75 years. The mean (SD) body mass index of the study participants was 26.7 (3.6). Twelve patients were excluded from the study because the follow-up US by the US technologist had not been completed. Therefore, the final sample size was 16 participants. 
The mean (SD) difference between student and technologist aortic US measurements was −0.15 cm (0.23) (t=−1.38; P=.09). None of the individuals screened in this study met the criteria for an aortic aneurysm (>3.0 cm), with the largest aorta scanned by experts measuring 2.86 cm (Table). The readings produced by osteopathic medical students in this study had a very high degree of agreement with the readings obtained by the technologist. The largest difference between a student's measurement and the technologist's measurement was 0.64 cm. 
Table.
Results for Abdominal Aorta Measurements Taken by Osteopathic Students Compared With an Experienced Technologist (N=16)
Mean (SD) Measurement, cma Difference Between Means (SD),c cm
Participant Body Mass Indexb Osteopathic Student US Technologist
1 21.0 2.2 (0.6) 2.1 (0.2) 0.2 (0.1)
2 21.0 1.8 (0.1) 2.2 (0.2) 0.4 (0.3)
3 29.7 2.4 (0.4) 1.7 (0.3) 0.6 (0.5)
4 27.5 2.2 (0.5) 1.9 (0.1) 0.4 (0.3)
5 27.4 1.8 (0.3) 2.0 (0.1) 0.2 (0.1)
6 32.2 1.6 (0) 1.8 (0.1) 0.2 (0.1)
7 30.0 1.7 (0.4) 1.8 (0.5) 0.1 (0.1)
8 26.0 1.4 (0.4) 2.0 (0.2) 0.6 (0.4)
9 23.6 1.9 (0.1) 2.0 (0.8) 0.1 (0.1)
10 26.9 2.2 (0.4) 2.1 (0.5) 0.1 (0.1)
11 30.1 2.0 (0.5) 2.5 (0.6) 0.6 (0.4)
12 24.1 1.5 (0.5) 2.1 (0.5) 0.6 (0.4)
13 28.3 1.8 (0.2) 2.1 (0.5) 0.3 (0.2)
14 28.0 2.6 (0.5) 2.9 (0.7) 0.3 (0.2)
15 30.9 1.7 (0.4) 2.2 (0.5) 0.5 (0.3)
16 21.2 2.1 (0.3) 1.9 (0.6) 0.2 (0.1)

a Means (SDs) were calculated from dimensions at 3 sites: celiac axis, just distal to the renal arteries, and just above the iliac bifurcation.

b Mean (SD) body mass index, 26.7 (3.6).

c Mean difference between means (SD), −0.15 cm (0.23) cm.

View Large
Table.
Results for Abdominal Aorta Measurements Taken by Osteopathic Students Compared With an Experienced Technologist (N=16)
Mean (SD) Measurement, cma Difference Between Means (SD),c cm
Participant Body Mass Indexb Osteopathic Student US Technologist
1 21.0 2.2 (0.6) 2.1 (0.2) 0.2 (0.1)
2 21.0 1.8 (0.1) 2.2 (0.2) 0.4 (0.3)
3 29.7 2.4 (0.4) 1.7 (0.3) 0.6 (0.5)
4 27.5 2.2 (0.5) 1.9 (0.1) 0.4 (0.3)
5 27.4 1.8 (0.3) 2.0 (0.1) 0.2 (0.1)
6 32.2 1.6 (0) 1.8 (0.1) 0.2 (0.1)
7 30.0 1.7 (0.4) 1.8 (0.5) 0.1 (0.1)
8 26.0 1.4 (0.4) 2.0 (0.2) 0.6 (0.4)
9 23.6 1.9 (0.1) 2.0 (0.8) 0.1 (0.1)
10 26.9 2.2 (0.4) 2.1 (0.5) 0.1 (0.1)
11 30.1 2.0 (0.5) 2.5 (0.6) 0.6 (0.4)
12 24.1 1.5 (0.5) 2.1 (0.5) 0.6 (0.4)
13 28.3 1.8 (0.2) 2.1 (0.5) 0.3 (0.2)
14 28.0 2.6 (0.5) 2.9 (0.7) 0.3 (0.2)
15 30.9 1.7 (0.4) 2.2 (0.5) 0.5 (0.3)
16 21.2 2.1 (0.3) 1.9 (0.6) 0.2 (0.1)

a Means (SDs) were calculated from dimensions at 3 sites: celiac axis, just distal to the renal arteries, and just above the iliac bifurcation.

b Mean (SD) body mass index, 26.7 (3.6).

c Mean difference between means (SD), −0.15 cm (0.23) cm.

×
Discussion
Our findings support the hypothesis that osteopathic medical students can accurately measure abdominal aortic dimensions using a handheld US device after brief hands-on training. Based on the t test results, no statistically significant difference was found in aortic measurements between the osteopathic medical students and the US technologist. 
Our findings reflect those of similar investigations. Bonnafy et al4 conducted AAA screenings on hospitalized patients in France using handheld US devices operated by medical students and found the mean difference between the measurements to be 0.1 cm, with an intraclass correlation coefficient of greater than 0.91. A study in New Zealand by Nguyen et al9 trained 3 novices (a medical student, a newly employed vascular technologist, and a physical education graduate) to conduct AAA screenings and found that these novices obtained coronal measurements within 0.5 cm of the measurements of experienced vascular US technologists 85% to 97% of the time. Although the French study mentioned using a handheld US device, the study in New Zealand used a laptop-based machine. Also, in the French study, 2 patients were found to have an AAA, which the medical students detected in concordance with the experts.4 Thus, considering both the current cohort and the French cohort of medical students were able to obtain measurements with no statistically significant difference, we would expect the osteopathic medical students in our cohort to accurately identify AAAs. 
Additionally, our cohort is unique because, to our knowledge, no similar studies have been conducted using osteopathic medical students as AAA investigators. The integration of US in medical education in the United States is highly variable. Bahner et al14 conducted a survey in 2014 and found that of 134 allopathic medical schools, 79% of schools agreed that US should be part of the medical school curriculum, but few respondents (18.6%) reported that it was a priority at their institutions, with lack of space and lack of financial support being barriers to integration of US. Furthermore, Dinh et al15 conducted a survey in 2016 of 173 US medical schools (both allopathic and osteopathic) and revealed that 48 schools (28%) reported having a required integrated US curriculum. The Rocky Vista University College of Osteopathic Medicine created a 4-year integrated US curriculum in 2015, and a review of the curriculum was conducted in 2016.16 Their review revealed students’ feedback to be positive, including an appreciation for the early exposure to US. Students also appreciated the repetition of concepts through the integration of hands-on US connecting with anatomy currently covered in systems courses.16 However, this study lacked quantitative measures of directly testing students’ proficiency aside from written questions containing US images.16 More quantitative measures could be a focus for future studies that evaluate the implementation of US into the medical school curriculum. 
Rural and county clinics have to refer patients to facilities with radiology capabilities to accomplish AAA screenings, which could result in lack of follow-up and missed screening opportunities. If medical students and primary care physicians were trained to conduct in-office aortic diameter measurements, it could result in increased screening opportunities and possibly reduced AAA-related mortality. 
Limitations
The US training provided to students was 8 hours. A potential bias for this study is that the student investigators self-identified as enthusiastic about US. Students with less interest in US may not have had the same level of outcomes when compared with the experienced US technologist as this student cohort. Also, 3 students independently performed each US screening, contributing to interobserver variability, which was not controlled for. Conducting the same study with multiple students evaluating each participant may yield different results. 
In addition, the name of the technologist performing secondary screenings at the Sutter Solano Radiology Department was not available, and, thus, no intraobserver variability was measured. Furthermore, the majority of the participants were either overweight or obese, which contributed to scanning difficulty. However, the accuracy of the measurements was not compromised. Another limitation is that this study's cohort did not include any cases of AAA, with the largest aorta measuring 2.86 cm (<3.0 cm cutoff for AAA). Last, we lost many patients because of problems with follow-up, which reduced our sample size. Conducting the same study in a different geographic area may yield different results with a higher rate of participation in the follow-up phase. 
Future Research
A larger cohort is needed to ascertain whether osteopathic medical students can accurately screen for AAA via US in a primary care setting. A larger cohort will have greater variability in aortic diameters, thus helping to further test the screening accuracy. In a similar study,4 a safe approach when training novices would require an expert ultrasonographer when the measured abdominal aortic diameter exceeds 26 mm, in order to not miss small AAAs (≥3.0 cm), which require further follow-up. This recommendation may be useful for future screening protocols and studies. Additionally, future studies might evaluate the differences, or lack thereof, in screening accuracies between allopathic medical students, osteopathic medical students, and other health profession students. 
Conclusion
Osteopathic medical students can be trained in US and can accurately measure abdominal aortic dimensions with limited US experience using a handheld US device with no statistically significant difference compared with experts. However, further studies are needed to assess the ability of osteopathic medical students to accurately measure AAAs, as no participants in this study met the criteria for AAA. With less than 50% of patients at risk for AAA being screened using US,1 training medical students (osteopathic and allopathic, under supervision), residents, and primary care physicians to perform accurate in-office screenings, could potentially reduce AAA-related mortality. Osteopathic medical schools should consider US training, including aortic diameter measurement, within their individual curriculum.18 
Author Contributions
All authors provided substantial contributions to conception and design, acquisition of data, or analysis and interpretation of data; all authors drafted the article or revised it critically for important intellectual content; all authors gave final approval of the version of the article to be published; and all authors agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. 
Acknowledgments
We thank Abraham Pera, DO, Robert Armstrong, DO, and Jay H. Shubrook, DO, for their technical assistance. 
References
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Table.
Results for Abdominal Aorta Measurements Taken by Osteopathic Students Compared With an Experienced Technologist (N=16)
Mean (SD) Measurement, cma Difference Between Means (SD),c cm
Participant Body Mass Indexb Osteopathic Student US Technologist
1 21.0 2.2 (0.6) 2.1 (0.2) 0.2 (0.1)
2 21.0 1.8 (0.1) 2.2 (0.2) 0.4 (0.3)
3 29.7 2.4 (0.4) 1.7 (0.3) 0.6 (0.5)
4 27.5 2.2 (0.5) 1.9 (0.1) 0.4 (0.3)
5 27.4 1.8 (0.3) 2.0 (0.1) 0.2 (0.1)
6 32.2 1.6 (0) 1.8 (0.1) 0.2 (0.1)
7 30.0 1.7 (0.4) 1.8 (0.5) 0.1 (0.1)
8 26.0 1.4 (0.4) 2.0 (0.2) 0.6 (0.4)
9 23.6 1.9 (0.1) 2.0 (0.8) 0.1 (0.1)
10 26.9 2.2 (0.4) 2.1 (0.5) 0.1 (0.1)
11 30.1 2.0 (0.5) 2.5 (0.6) 0.6 (0.4)
12 24.1 1.5 (0.5) 2.1 (0.5) 0.6 (0.4)
13 28.3 1.8 (0.2) 2.1 (0.5) 0.3 (0.2)
14 28.0 2.6 (0.5) 2.9 (0.7) 0.3 (0.2)
15 30.9 1.7 (0.4) 2.2 (0.5) 0.5 (0.3)
16 21.2 2.1 (0.3) 1.9 (0.6) 0.2 (0.1)

a Means (SDs) were calculated from dimensions at 3 sites: celiac axis, just distal to the renal arteries, and just above the iliac bifurcation.

b Mean (SD) body mass index, 26.7 (3.6).

c Mean difference between means (SD), −0.15 cm (0.23) cm.

View Large
Table.
Results for Abdominal Aorta Measurements Taken by Osteopathic Students Compared With an Experienced Technologist (N=16)
Mean (SD) Measurement, cma Difference Between Means (SD),c cm
Participant Body Mass Indexb Osteopathic Student US Technologist
1 21.0 2.2 (0.6) 2.1 (0.2) 0.2 (0.1)
2 21.0 1.8 (0.1) 2.2 (0.2) 0.4 (0.3)
3 29.7 2.4 (0.4) 1.7 (0.3) 0.6 (0.5)
4 27.5 2.2 (0.5) 1.9 (0.1) 0.4 (0.3)
5 27.4 1.8 (0.3) 2.0 (0.1) 0.2 (0.1)
6 32.2 1.6 (0) 1.8 (0.1) 0.2 (0.1)
7 30.0 1.7 (0.4) 1.8 (0.5) 0.1 (0.1)
8 26.0 1.4 (0.4) 2.0 (0.2) 0.6 (0.4)
9 23.6 1.9 (0.1) 2.0 (0.8) 0.1 (0.1)
10 26.9 2.2 (0.4) 2.1 (0.5) 0.1 (0.1)
11 30.1 2.0 (0.5) 2.5 (0.6) 0.6 (0.4)
12 24.1 1.5 (0.5) 2.1 (0.5) 0.6 (0.4)
13 28.3 1.8 (0.2) 2.1 (0.5) 0.3 (0.2)
14 28.0 2.6 (0.5) 2.9 (0.7) 0.3 (0.2)
15 30.9 1.7 (0.4) 2.2 (0.5) 0.5 (0.3)
16 21.2 2.1 (0.3) 1.9 (0.6) 0.2 (0.1)

a Means (SDs) were calculated from dimensions at 3 sites: celiac axis, just distal to the renal arteries, and just above the iliac bifurcation.

b Mean (SD) body mass index, 26.7 (3.6).

c Mean difference between means (SD), −0.15 cm (0.23) cm.

×