Ankle brachial index performance among internal medicine residents

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1 Ankle brachial index performance among internal medicine residents Vascular Medicine 15(2) The Author(s) 2010 Reprints and permission: sagepub.co.uk/journalspermission.nav DOI: / X Matthew F Wyatt 1, Chad Stickrath 1,2, Alap Shah 1,3, Alexandra Smart 1, James Hunt 1 and Ivan P Casserly 1,2 Abstract The ankle brachial index (ABI) is the standard test used in clinical practice to detect peripheral artery disease (PAD) and is a powerful predictor of adverse cardiovascular outcomes. This study sought to measure the baseline knowledge of the ABI test among a sample of internal medicine residents and to examine the impact of an educational intervention on performance of the test. A total of 29 residents were asked to perform three tasks, with the performance of each task being assessed using a point-based scoring system: measure an ABI on a normal volunteer (15 points), calculate the ABI based on data from a hypothetical patient (3 points), and interpret a range of ABI values (6 points). A standardized educational intervention was then provided and post-education performance was assessed for each task using the same scoring system. At baseline, 4% of residents correctly measured the ABI, 10% correctly calculated the ABI, and 45% correctly interpreted the ABI. Baseline performance was unaffected by year of residency training. Following the educational intervention, 50% of residents correctly measured the ABI, 75% correctly calculated the ABI, and 88% correctly interpreted the ABI. The mean score for the tasks of ABI measurement, calculation and interpretation between baseline and post-education were 4.6 ± 3 and 13.9 ± 1.6 (p < ), 1 ± 0.9 and 2.3 ± 1.2 (p = 0.002), and 4.9 ± 1.6 and 5.9 ± 0.3 (p = 0.008), respectively. In conclusion, baseline knowledge of the ABI test was poor among a sample of internal medicine residents. These results suggest that instruction regarding the ABI test is deficient in medical school and residency programs and requires action by those responsible for the education of medical students and residents. Keywords ankle brachial index; education; performance; peripheral artery disease Introduction Peripheral artery disease (PAD) refers to atherosclerotic disease of the lower extremities. 1 It is highly prevalent, affecting 8 12 million individuals in the United States, including more than 20% of individuals over the age of 70 years. 2 4 The presence of PAD may significantly impact a patient s quality of life by causing lifestyle-limiting claudication, or it may result in limb threat if the patient progresses to critical limb ischemia. 5 In addition, the diagnosis of PAD, even among asymptomatic individuals, predicts a significant risk of subsequent cardiovascular (CV) morbidity and mortality. 6 8 The ankle brachial index (ABI) is the accepted screening test used in clinical practice to diagnose PAD. 9 The method for measuring, calculating, and interpreting the ABI has been standardized By virtue of its ability to diagnose PAD (i.e. ABI 0.90), the ABI has also been shown to be an important addition to conventional CV risk factors in predicting overall and cardiovascular-related mortality. 6 8 This is particularly important in asymptomatic individuals who do not have documented atherosclerosis in other vascular territories, as the presence of PAD on the basis of an abnormal ABI provides an opportunity to initiate appropriate preventive medical therapy. Despite these data, a significant proportion of individuals with PAD (over 44%) remain undiagnosed in clinical practice. 2,14 Based on our experience, a fundamental lack of knowledge and technical expertise exists among internal medicine physicians with regard to ABI measurement, calculation, and interpretation. This lack of knowledge represents one of the barriers to use of the ABI for diagnosing 1 University of Colorado Denver, Aurora, CO, USA 2 Denver Veterans Administration Medical Center, Denver, CO, USA 3 Rush University Medical Center, Chicago, IL, USA Corresponding author: Ivan P Casserly University of Colorado Denver Anschutz Medical Campus Leprino Office Building, East 17th Avenue PO Box 6511, Campus Box B-132 Aurora, CO 80045, USA ivan.casserly@ucdenver.edu

2 100 Vascular Medicine 15(2) appropriate sized cuff for each arm and the right leg (1 point each); using the Doppler probe to attempt to obtain pressures from the right and left brachial arteries and the right dorsalis pedis and posterior tibial arteries (1 point each); attempting to obtain a pressure measurement from both arms and both tibial arteries (1 point each); and verbally recording a systolic pressure measurement within 5 mmhg of the onset of the Doppler signal for the right and left brachial arteries and the right dorsalis pedis and posterior tibial arteries (1 point each). A maximum score of 15 was awarded for this task. Figure 1. Photograph of tools provided to participants in order to perform ankle brachial index (ABI) measurement, including: small arm cuff, large leg cuff, 8 MHz Doppler probe, gel, stethoscope. PAD and stratifying CV risk, and has important implications for health care systems that seek to use the ABI effectively in managing symptomatic and asymptomatic patients with PAD. This study sought to assess the competence of a group of internal medicine residents in measuring, calculating, and interpreting the ABI, and to examine the impact of an educational intervention on improving subsequent performance. Methods The study was approved by the University of Colorado Institutional Review Board with no external funding. Internal medicine residents from all three years of the University of Colorado Internal Medicine Residency were invited, via a residency-wide from the chief medical resident, to participate in a study involving a common clinical screening tool. Baseline assessment Following consent, each resident was asked to perform three tasks. 1. ABI measurement. In a standardized environment, participants were given written instructions directing them to perform an ABI measurement for the right lower extremity of a healthy subject. The equipment in Figure 1 was provided for each participant, and included adult medium and large sized blood pressure cuffs, an 8 MHz Doppler ultrasound probe, ultrasound gel, and a stethoscope. Performance was observed and scored by a trained observer (MFW) using a standardized template developed by the authors (MFW and IPC) for use in this study (Appendix 1). Points were awarded for correct completion of critical elements of ABI measurement. These included: using the 2. ABI calculation. Participants were then given a worksheet listing the upper and lower extremity blood pressure data from a hypothetical patient with PAD, and instructed in writing to select the appropriate numerator and denominator required to calculate the right and left ABI for the hypothetical patient (Appendix 2). One point was awarded for each of the following: selection of the higher of the two pedal pressures for both the right and left ABI; selection of the higher of the two brachial pressures for both the right and left ABI; and use of an ankle pressure as the numerator and a brachial pressure as the denominator for both the right and left ABI. A maximum score of 3 was awarded for this task. 3. ABI interpretation. Next, participants were given a worksheet listing six ABI values and instructed in writing to match each ABI value with the appropriate interpretation (Appendix 3; based on current ACC/AHA guidelines Appendix 4). A point was awarded for each correct interpretation (maximum score of 6). Values between 0.91 and 0.99 are considered equivocal and were purposely not included on the interpretation worksheet. In addition, values between 1.30 and 1.40 were not included due to variabi lity in the published literature regarding the appropriate threshold for diagnosing non-compressible tibial vessels. Educational intervention Approximately 1 month after the baseline evaluation, each participant received feedback on their individual errors in ABI measurement, calculation, and interpretation, and on the most common errors of the study group. All participants were then provided with a standardized educational session incorporating an ABI measurement demonstration performed by an experienced vascular specialist (IC), review of the standardized method for ABI calculation, and a review of the ACC/AHA guidelines for ABI interpretation (educational session available at: mms:\\essvideo.uchsc. edu\public\abitutorial.wmv). Repeat assessment Following the educational intervention, each participant repeated the three tasks as previously described for the baseline assessment. The same trained observer (MFW) was present and the same scoring tools were used to assess performance. A different set of limb pressures and ABI measurements were given for the ABI calculation and interpretation tasks, respectively.

3 Wyatt MF et al. 101 Table 1. Errors in ankle brachial index (ABI) measurement at baseline Measurement error N [%] Baseline (n = 29) Post-education (n = 24) Failure to use Doppler to assess brachial pressures 25 [86] 1 [4] Failure to assess both pedal vessels (i.e. DP and PT) 24 [83] 0 [0] Failure to assess both brachial pressures 23 [79] 0 [0] Failure to accurately record Doppler signal from brachial or pedal artery 12 [60] a 12 [50] Use of small arm cuff to assess pedal pressures 15 [52] 1 [4] Incorrect placement of ankle cuff over body of calf muscles 14 [48] 2 [8] Failure to use Doppler to assess pedal pressures 9 [31] 0 [0] Use of large leg cuff to assess brachial pressures 4 [14] 1 [4] Assessment of radial artery pressure instead of brachial pressure 1 [4] 0 [0] DP, dorsalis pedis; PT, posterior tibial. a Only 20 of 29 participants utilized the Doppler ultrasound at baseline. Accordingly, this item is calculated for n = 20 rather than n = 29. % Correct Of the initial cohort of 29 residents, 24 [83%] received the educational intervention and performed the repeat evaluation. These included 13 first-year residents, eight second-year residents, and three third-year residents. Baseline results include performance data from the entire cohort of 29 residents who completed the baseline assessment. Post-educational intervention results, including comparison of baseline and repeat performance scores, only include performance data from the 24 residents who also completed the repeat assessment Statistical analysis Continuous variables are reported as means with standard deviation. Categorical variables are reported as numbers with percentages. A paired t-test was used to compare the difference between baseline and post-education scores for each task. To assess whether a significant difference in baseline ABI performance existed between first-year residents and second/thirdyear residents, an unpaired t-test was used to compare scores for each task between the two groups. All tests were performed using SAS version 9.1 (Cary, NC, USA). Results 4 10 Measurement Calculation Interpretation Baseline Post-Education Figure 2. Percent of participants who completed the ankle brachial index (ABI) measurement, calculation, and interpretation tasks correctly at baseline and following the educational intervention. A total of 29 internal medicine residents volunteered for the study and completed the baseline ABI performance evaluation. Participants included 15 first-year residents, 10 secondyear residents, and four third-year residents. A minority of participants (35%, 10 of 29) reported previous practical experience performing an ABI. ABI measurement Baseline. At baseline evaluation, one participant [4%] completed the ABI measurement task without an error. The mean baseline measurement score for all participants was 4.55 ± 2.95, range ABI measurement errors and their frequency are listed in Table 1. The most common errors included the following: use of the stethoscope rather than the Doppler ultrasound probe to measure the brachial artery systolic pressure; failure to assess pressure from both pedal vessels in the right leg; and failure to acquire systolic pressures from both brachial arteries. Post-educational intervention. Following the educational intervention, the number of residents who completed the ABI measurement task without an error increased to 12 [50%] (Figure 2). The mean repeat measurement score for all participants was ± 1.60, which was significantly improved compared with the baseline score (p < ). ABI calculation Baseline. At baseline evaluation, three participants [10%] correctly calculated the right and left ABI using the given blood pressure data. The mean baseline calculation score for all participants was 1.00 ± 0.93, range 0 3. ABI calculation errors and their frequency are listed in Table 2. Common errors included the use of the right and left brachial pressures as the denominator for the right and left ABI calculation, respectively, and failure to use the higher of the two pedal pressures as the numerator in the ABI calculation.

4 102 Vascular Medicine 15(2) Table 2. Errors in ankle brachial index (ABI) calculation at baseline Calculation error N [%] Baseline Post-education (n = 29) (n = 24) Use of lower/ipsilateral 20 [69] 1 [4] brachial pressure Exclusive use of PT 20 [69] 0 [0] or DP pressure Reversal of ABI fraction 9 [31] 4 [17] (i.e. brachial ankle) Other mathematical error 2 [7] 1 [4] PT, posterior tibial; DP, dorsalis pedis. Post-educational intervention. Following the educational intervention, 18 participants [75%] correctly calculated the ABI (Figure 2). The mean repeat calculation score for all participants was 2.33 ± 1.24, which was significantly improved compared to the baseline score (p = ). ABI interpretation Baseline. At baseline evaluation, 13 participants [45%] correctly interpreted all six ABI values. The mean baseline interpretation score for all participants was 4.86 ± 1.57, range 0 6. ABI interpretation errors and their frequency are listed in Table 3. The errors were scattered across the entire range of ABI values. Post-educational intervention. Following the educational intervention, 21 participants [88%] correctly interpreted all six ABI values (Figure 2). The mean repeat interpretation score for all participants was 5.88 ± 0.34, which was significantly improved compared with the baseline score (p = ). Impact of level of training Baseline performance results for each task were compared between first-year internal medicine residents (n = 15) and second/third-year residents (n = 14). Among first-year and second/third-year residents, three [20%] and seven [50%] residents reported previous experience of performing an ABI, respectively. The mean scores for each task for the first-year and second/ third-year resident groups are shown in Table 4. No statistically significant performance difference existed between the two groups for any task. Discussion This study documents a remarkably poor level of baseline competency with regard to ABI measurement, calculation, and interpretation among a sample of residents from an internal medicine residency at an academic center in the United States. From a total of 29 residents, only one [4%] correctly completed all elements required to measure an ABI, three [10%] calculated the ABI correctly based on data from a hypothetical patient, and 13 [45%] provided the correct interpretation of a range of ABI values. No significant difference existed between the performance of first-year versus second/third-year residents. Following an intervention that combined direct feedback to participants with an internet video that included demonstration of an ABI measurement and instruction regarding ABI calculation and interpretation, there was a significant improvement in performance, but 50% of residents continued to make fundamental errors in the ABI measurement task. The findings of this study underscore our clinical impression that a significant lack of knowledge exists among internal medicine residents regarding the ABI test. In fact, our experience suggests that the performance of the internal medicine residents in this study would not differ significantly Table 3. Errors in ankle brachial index (ABI) interpretation at baseline Interpretation error N [%] Baseline (n = 29) Post-education (n = 24) Misinterpret ABI = 1.5 as normal 10 [35] 0 [0] Misinterpret ABI = 0.6 as severe PAD, or non-compressible 5 [17] 0 [0] Misinterpret ABI = 0.3 as moderate PAD, or non-compressible 5 [17] 0 [0] Misinterpret ABI = 1.2 as mild PAD, or non-compressible 4 [14] 2 [8] Misinterpret ABI = 1.0 as mild or moderate PAD 4 [14] 0 [0] Misinterpret ABI = 0.8 as severe PAD, or normal 3 [10] 1 [4] PAD, peripheral artery disease. Table 4. Comparison of mean baseline scores for each task between first-year residents and second/third-year residents Task 1st year residents (n = 15) 2nd/3rd year residents (n = 14) p-value ABI measurement score (mean ± SD) 3.8 ± ± ABI calculation score (mean ± SD) 0.8 ± ± ABI interpretation score (mean ± SD) 5.1 ± ± ABI, ankle brachial index.

5 Wyatt MF et al. 103 from that of fully trained internal medicine physicians, surgical residents, and even cardiologists. The explanation for this lack of knowledge in this cohort appears to be a lack of instruction: only a third of residents reported prior experience in performing an ABI, and significant improvements in performance were observed following a relatively modest educational intervention. Since the performance of first-year residents was no different from second/third-year residents, it appears that instruction regarding the ABI test is deficient in both the medical schools of origin of our residents and in the internal medicine residency at our institution. Given the importance of the ABI in clinical practice, the absence of sufficient instruction for trainees is disappointing. An increasing body of literature supports the use of the ABI as a powerful predictor of adverse CV events 7,8 and, when added to the Framingham Risk Score, the ABI has been shown to result in a significant reclassification of risk, with associated treatment implications, for approximately 36% of females and 19% of males. 6 In addition, the ABI is the standard screening tool for evaluation of patients with symptoms suggestive of PAD. 9 As such, this tool should be an important part of the physical examination of selected at-risk patients by all internal medicine physicians. The current study highlights a deficiency that needs to be addressed by those responsible for the education of medical students and internal medicine residents. Training should include practical instruction on performing an ABI as well as didactic teaching on ABI calculation and interpretation guidelines. Although resident ABI measurement performance did improve following the educational intervention, the fact that only 50% performed the task without an error suggests repeated instruction is required to achieve high levels of competency. At our institution, the ABI instructional video has been made available to all medical students and residents online as a first step in addressing this important training. Moving forward, we believe that mandatory rotation of internal medicine residents through a vascular clinic where residents receive practical instruction regarding the ABI test and get to repeatedly practice the test in patients offers the best solution to addressing the limitation in medical school education and residency training highlighted by the current study. Any discussion of barriers to the effective use of the ABI in clinical practice needs to include an awareness of the findings of this study, and the possible extrapolation of these findings to the broad population of internal medicine physicians. While time constraints in busy clinics and lack of reimbursement have been reported as major hurdles in employing this tool, 15 none of the benefits of the ABI can be realized if physicians lack the knowledge to perform this test and interpret the result. Even in situations where allied health staff carries out the actual test, the physician is ultimately responsible for making sure it is completed correctly. Limitations Several limitations to this study should be considered. Our sample population was small (29 individuals) and restricted to internal medicine residents at a single academic institution, although it should be noted that these residents did receive their medical education from several medical schools within the United States. On that basis, it is possible that our findings are not generalizable to the broader population of internal medicine residents in the United States. Owing to busy resident schedules, a period of 2 4 weeks was accepted for the interval between the educational intervention and the repeat assessment. It is possible that participants with longer follow-up intervals scored more poorly than participants with shorter intervals, and that our results would be different had uniform intervals been possible. Furthermore, five participants were lost to follow-up due to the inability to schedule a timely repeat evaluation. Finally, only four third-year residents volunteered for the study. As third-year residents have more experience than firstand second-year residents, it is possible that a study composed of a larger number of third-year residents may show different results. A larger, multi-center trial designed along the lines of this pilot study is warranted to more accurately evaluate the knowledge of a broad population of internal medicine residents in the United States regarding the ABI test. Summary and conclusions In conclusion, this study demonstrated a poor baseline level of competency among a sample of internal medicine residents from a single academic institution in the United States with regard to ABI measurement, calculation, and interpretation. In this cohort, a lack of specific instruction in medical school and internal medicine residency appears to be the root cause for this lack of competency. Given the importance of the ABI in assessing patients with symptoms of PAD and providing an inexpensive and powerful predictor of adverse CV events in the population, further studies to assess whether these findings truly reflect the general level of knowledge of internal medicine residents in the United States regarding the ABI test are warranted. 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6 104 Vascular Medicine 15(2) cardiovascular events and mortality: a meta-analysis. JAMA 2008; 300: Heald CL, Fowkes FG, Murray GD, Price JF. Risk of mortality and cardiovascular disease associated with the ankle brachial index: systematic review. Atherosclerosis 2006; 189: Doobay AV, Anand SS. Sensitivity and specificity of the ankle brachial index to predict future cardiovascular outcomes: a systematic review. Arterioscler Thromb Vasc Biol 2005; 25: Begelman SM, Jaff MR. Noninvasive diagnostic strategies for peripheral arterial disease. Cleve Clin J Med 2006; 73(suppl 4): S Hirsch AT, Haskal ZJ, Hertzer NR, et al. ACC/AHA 2005 Practice Guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (Writing Committee to Develop Guidelines for the Management of Patients With Peripheral Arterial Disease): endorsed by the American Association of Cardiovascular and Pulmonary Rehabilitation; National Heart, Lung, and Blood Institute; Society for Vascular Nursing; TransAtlantic Inter-Society Consensus; and Vascular Disease Foundation. Circulation 2006; 113: e Sacks D, Bakal CW, Beatty PT, et al. Position statement on the use of the ankle brachial index in the evaluation of patients with peripheral vascular disease. A consensus statement developed by the Standards Division of the Society of Interventional Radiology. J Vasc Interv Radiol 2003; 14(9 Pt 2): S Caruana MF, Bradbury AW, Adam DJ. The validity, reliability, reproducibility and extended utility of ankle to brachial pressure index in current vascular surgical practice. Eur J Vasc Endovasc Surg 2005; 29: Fleck CA. Measuring ankle brachial pressure index. Adv Skin Wound Care 2007; 20: , Belch JJ, Topol EJ, Agnelli G, et al. Critical issues in peripheral arterial disease detection and management: a call to action. Arch Intern Med 2003; 163: Mohler ER 3rd, Treat-Jacobson D, Reilly MP, et al. Utility and barriers to performance of the ankle brachial index in primary care practice. Vasc Med 2004; 9:

7 Wyatt MF et al. 105 Appendix 1. ABI measurement Instruction: Perform the measurements required to calculate a RIGHT ankle brachial index (ABI) for this patient. You have been provided with all the necessary tools. You do not need to calculate the ABI using the measurements you obtain, nor do you need to make a diagnosis. Scoring sheet Element of ABI measurement Arm A. Use of arm cuff 1 B. Use of Doppler probe to acquire systolic pressure from brachial vessels 1 (i) Right brachial artery (a) Doppler signal obtained from right brachial artery 1 (ii) Left brachial artery (a) Doppler signal obtained from left brachial artery 1 C. Systolic pressure acquired from both brachial arteries 1 Right leg A. Use of leg cuff 1 B. Correct placement of cuff over lower leg 1 C. Use of Doppler probe to acquire systolic pressure from tibial vessels 1 (i) Dorsalis pedis artery (a) Doppler signal obtained from right dorsalis pedis artery 1 (ii) Posterior tibial artery (a) Doppler signal obtained from right posterior tibial artery 1 D. Systolic pressure acquired from both pedal arteries 1 Total score 15 Score Appendix 2. ABI calculation Instruction: Mr Smith is a 65-year-old male with diabetes mellitus who presents to your office for a routine physical examination. You decide to perform an ankle brachial index (ABI). The blood pressure measurements from the exam are shown below. Calculate the right ABI for Mr Smith and present your answer as the value for the numerator over the value for the denominator. Artery Right brachial 130 Left brachial 120 Right dorsalis pedis 128 Right posterior tibial 115 Left dorsalis pedis 110 Left posterior tibial 117 Systolic blood pressure (mmhg) Appendix 3. ABI interpretation Instruction: Match the ankle brachial index (ABI) value in the left column with the correct diagnosis listed in the right column. Each diagnosis selection may be used more than once. 1. ABI = 1.5 A. Normal 2. ABI = 1.2 B. Mild to moderate peripheral artery disease 3. ABI = 1.0 C. Severe peripheral artery disease 4. ABI = 0.8 D. Non-compressible tibial arteries 5. ABI = ABI = 0.3 Scoring 1 point for each correct answer. Maximum score of 6. Scoring sheet Element of ABI calculation Select higher pedal pressure for both right and 1 left ABI Select higher brachial pressure for both right 1 and left ABI Use pedal pressure as numerator and brachial 1 pressure as denominator for both right and left ABI Total score 3 Score Appendix 4. ACC/AHA guidelines for ABI interpretation ABI Interpretation 1.3 Non-compressible Normal Equivocal Mild-to-moderate PAD 0.4 Severe PAD ABI, ankle brachial index; PAD, peripheral artery disease.