Point-of-Care Ultrasound Performed by a Medical Student Compared to Physical Examination by Vascular Surgeons in the Detection of Abdominal Aortic Aneurysms

Abstract

Background: The use of point-of-care ultrasound (POCUS) has become increasingly prevalent in medical practice as a non-invasive tool for focused bedside diagnosis. Consequently, some medical schools have begun implementing POCUS training as a standard in their medical school curriculum. The feasability and value of introducing POCUS training at the medical student level to screen for abdominal aortic aneurysms (AAA) should be explored. Given this, the objective of our study was to determine the test characteristics of point-of-care ultrasonography performed by a medical student versus physical examination by vascular surgeons compared to a gold standard reference scan for the detection of AAAs.

Methods: We conducted a prospective, observer-blinded study recruiting patients from an outpatient vascular surgery clinic. Participants were screened for AAAs by standardized physical examination by a blinded vascular surgeon, followed by a POCUS examination by a blinded medical student. The student underwent prior training by a vascular sonographer and emergency physician on 60 patients (16 were supervised). Ultrasonography was used to visualize and measure the proximal, mid, and distal aortic diameters. The maximal aortic diameter was noted and compared with measurements obtained by the reference scan (computed tomography scan or vascular sonographer-performed ultrasound). Reference scans were completed within 3 months of the recruitment visit.

Results: A total of 57 patients were enrolled over a 5-month period between October 2015 and March 2016. Mean age of recruited patients was 71 years, and 61% were male. Mean body mass index was 27.9 ± 4.3, and mean waist-to-hip ratio was 0.96 ± 0.10. Sixteen AAAs were detected by the reference scan, with an average maximal aortic diameter of 44.9 mm. Physical examination by a vascular surgeon detected 11 of 16 AAAs with 2 false positives (sensitivity and specificity of 66.7% [95% confidence interval [CI], 38.4-88.2] and 94.4% [95% CI, 81.3-99.3], respectively). POCUS detected 15 of 16 AAAs (sensitivity and specificity of 93.3% [95% CI, 68.1-99.8] and 100% [95% CI, 88.4-100], respectively). Seven of the 64 POCUS scans were indeterminate (>1 cm of the aorta was not visualized). Average time to conduct the physical examination was 35 sec versus 4.0 min for point-of-care ultrasonography. There was a strong linear correlation (R² = 0.95) between maximal aortic diameter measured by point-of-care ultrasonography versus reference scan with a mean absolute difference of 2.6 mm.

Conclusion: Point-of-care ultrasonography performed by a medical student is highly accurate and more effective in detecting AAAs than physical examination by vascular surgeons. The introduction of POCUS training at the medical student level and its wide-scale implementation as an extension to physical examination may lead to improved detection of AAAs.