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The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS).
BMC Cardiovasc Disord. 2006;6:7
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BACKGROUND: A low ankle-brachial index (ABI) is associated with increased risk of coronary heart disease, stroke, and death. Regression model parameter estimates may be biased due to measurement error when the ABI is included as a predictor in regression models, but may be corrected if the reliability coefficient, R, is known. The R for the ABI computed from DINAMAP readings of the ankle and brachial SBP is not known.
METHODS: A total of 119 participants in both the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS) had repeat ABIs taken within 1 year, using a common protocol, automated oscillometric blood pressure measurement devices, and technician pool.
RESULTS: The estimated reliability coefficient for the ankle systolic blood pressure (SBP) was 0.68 (95% CI: 0.57, 0.77) and for the brachial SBP was 0.74 (95% CI: 0.62, 0.83). The reliability for the ABI based on single ankle and arm SBPs was 0.61 (95% CI: 0.50, 0.70) and the reliability of the ABI computed as the ratio of the average of two ankle SBPs to two arm SBPs was estimated from simulated data as 0.70.
CONCLUSION: These reliability estimates may be used to obtain unbiased parameter estimates if the ABI is included in regression models. Our results suggest the need for repeated measures of the ABI in clinical practice, preferably within visits and also over time, before diagnosing peripheral artery disease and before making therapeutic decisions.
OBJECTIVE: The ankle-brachial index, which is calculated by dividing ankle systolic blood pressure by brachial systolic blood pressure, is useful in diagnosing peripheral arterial disease. Consensus has not been reached, however, on a standard method for measuring ankle systolic blood pressure. This study evaluated two cuff-wrapping methods for measuring ankle systolic blood pressure, compared with intra-arterial pressure as a gold standard.
METHODS: Study participants were 24 consecutive adult patients who underwent surgery under general anesthesia at Kyoto Prefectural University Hospital in Japan between January and March 2002. Indirect ankle systolic blood pressure was measured in the posterior tibial artery using a Doppler device and two cuff-wrapping methods: spiral, and straight. Direct ankle systolic blood pressure was measured in the dorsalis pedis artery.
RESULTS: Mean difference in ankle systolic blood pressure between indirect and direct measurements (indirect minus direct) was 1.4 mmHg [standard deviation of the difference (SDd), 17.6 mmHg] with the straight method and -1.4 mmHg (SDd, 22.2 mmHg) with the spiral method. The limit of agreements (mean difference +/-2 SDd) and intraclass correlation coefficient between two observers were -17.6 to 20.1 mmHg and 0.94, respectively, for the straight method and -39.4 to 40.0 mmHg and 0.78, respectively, for the spiral method.
CONCLUSIONS: The straight method, the same cuff-wrapping method used for measuring brachial blood pressure, appears to represent a more suitable wrapping method because of better interobserver reproducibility. Accuracy and reproducibility of indirect ankle systolic blood pressure measurement, however, were not adequately improved by either of the wrapping methods.
Combined use of brachial-ankle pulse wave velocity and ankle-brachial index for fast assessment of arteriosclerosis and atherosclerosis in a community. Int J Cardiol. 2005 Jan;98(1):99-105
Chuang SY, Chen CH, Cheng CM, Chou P
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BACKGROUND: Pulse volume recordings and blood pressures at arms and ankles can be obtained automatically and simultaneously to allow fast measurements of the brachial-ankle pulse wave velocity and the ankle-brachial index. We applied this novel technique to assess the extent of arteriosclerosis and atherosclerosis in a community.
METHODS: A total of 1329 residents in Kinmen completed a health survey including interview, physical examination, blood test, and the measurements of brachial-ankle pulse wave velocity and ankle-brachial index in 10 working days.
RESULTS: Brachial-ankle pulse wave velocity was significantly related to age, systolic blood pressure, body mass index, waist circumference, ankle-brachial index, and fasting blood levels of glucose, triglyceride, high-density lipoprotein cholesterol, uric acid, and creatinine, and was significantly related to the 10-year risk of developing coronary heart disease estimated from the Framingham risk function. The prevalence of arteriosclerosis as defined by brachial-ankle pulse wave velocity values higher than the age and sex stratified references from the low risk subjects was 27.1% for men and 25.4% for women. The prevalence of atherosclerosis defined by ankle-brachial index <0.9 was 2.8% in men and 1.7% in women. In men but not in women, subjects with low ankle-brachial index had significantly greater risk for developing coronary artery disease than those with normal values.
CONCLUSIONS: Brachial-ankle pulse wave velocity and ankle-brachial index can be obtained simultaneously and quickly for the assessment of arteriosclerosis and atherosclerosis in a community.
Limitation of the resting ankle-brachial index in symptomatic patients with peripheral arterial disease. Vasc Med. 2006 Feb;11(1):29-33
Stein R, Hriljac I, Halperin JL, Gustavson SM, Teodorescu V, Olin JW
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Peripheral arterial disease (PAD) has been demonstrated to be prevalent in the primary care setting. However, it has also been shown to be unrecognized and under-treated. Owing to the association with cardiovascular disease it has been recommended to screen high-risk patients for PAD in the primary care setting using the ankle-brachial index (ABI). ABI has been demonstrated to be highly sensitive and specific in diagnosing PAD in patients with significant stenosis. However, the utility in patients with less severe stenosis and calcified vessels is in question. The aims of this study were to determine the diagnostic utility of measuring the ABI at rest in patients referred to the vascular laboratory for evaluation of suspected PAD, and to assess the added value of pulse volume recordings and post-exercise studies in patients with a normal ABI. A computerized vascular diagnostic laboratory database was queried for symptomatic outpatients referred for measurement of segmental blood pressure, the ABI or pulse volume recordings by physicians not specialized in the evaluation and management of patients with peripheral vascular disease. Of 707 patients undergoing outpatient physiologic arterial evaluations between February 1, 2003 and July 31, 2004, 396 met these inclusion criteria. Data recorded included resting ABI, ABI following treadmill exercise test and the presence of abnormal pulse volume recordings. The study population (n = 396) consisted of equal numbers of men and women (mean age 69 years, range 19-100 years). Among 396 studies, resting ABI values were normal in 183 (46.2%) and abnormal in 159 (40.2%). Of the 138 patients who underwent exercise testing, 84 had normal ABI readings at rest. In the 84 patients who had a normal ABI at rest and underwent exercise testing, the ABI fell below 0.9 after exercise in 26 (31%). Arterial non-compressibility was detected in 54 (13.6%) patients, whose average age was 67 years. Thirteen (24%) of those with non-compressible vessels had abnormal pulse volume recording (PVR) results, compared to five with normal resting ABI who had abnormal PVR findings (2.7%). In conclusion, this study demonstrated that nearly half of patients referred to the outpatient vascular laboratory because of suspected arterial disease had a normal resting ABI. While it is recommended that the ABI be measured at rest in patients at risk of PAD in primary care practice, these findings suggest that patients with symptoms of PAD should be more completely evaluated in a vascular laboratory. Furthermore, when the ABI is normal at rest in patients with symptoms of intermittent claudication, exercise testing is recommended to enhance the sensitivity for detection of PAD.
A new efficient trial design for assessing reliability of ankle-brachial index measures by three different observer groups. BMC Cardiovasc Disord. 2006;6:33
Endres HG, Hucke C, Holland-Letz T, Trampisch HJ
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BACKGROUND: The usual method of assessing the variability of a measure such as the ankle brachial index (ABI) as a function of different observer groups is to obtain repeated measurements. Because the number of possible observer-subject combinations is impractically large, only a few small studies on inter- and intraobserver variability of ABI measures have been carried out to date. The present study proposes a new and efficient study design. This paper describes the study methodology.
METHODS: Using a partially balanced incomplete block design, six angiologists, six primary-care physicians and six trained medical office assistants performed two ABI measurements each on six individuals from a group of 36 unselected subjects aged 65-70 years. Each test subject is measured by one observer from each of the three observer groups, and each observer measures exactly six of the 36 subjects in the group. Each possible combination of two observers occurs exactly once per patient and is not repeated on a second subject. The study involved four groups of 36 subjects (144), plus standbys.
RESULTS: The 192 volunteers present at the study day were similar in terms of demographic characteristics and vascular risk factors: mean age 68.6 +/- 1.7; mean BMI 29.1 +/- 4.6; mean waist-hip ratio 0.92 +/- 0.09; active smokers 12%; hypertension 60.9%; hypercholesterolemia 53.4%; diabetic 17.2%. A complete set of ABI measurements (three observers performing two Doppler measurements each) was obtained from 108 subjects. From all other subjects at least one ABI measurement was obtained. The mean ABI was 1.08 (+/- 0.13), 15 (7.9%) volunteers had an ABI < 0.9, and none had an ABI > 1.4, i.e. a ratio that may be associated with increased stiffening of the arterial walls.
CONCLUSION: This is the first large-scale study investigating the components of variability and thus reliability in ABI measurements. The advantage of the new study design introduced here is that only one sixth of the number of theoretically possible measurements is required to obtain information about measurement errors. Bland-Altman plots show that there are only small differences and no systematic bias between the observers from three occupational groups with different training backgrounds.
Measurement, calculation, and normal range of the ankle-arm index: a bibliometric analysis and recommendation for standardization. Ann Vasc Surg. 2006 Mar;20(2):282-92
Klein S, Hage JJ
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Since its introduction in 1950, a variety of methods of measurement and calculation have been used to establish the ankle-arm index (AAI). This has resulted in variations of its normal range and difficulty in comparing study results. Hence, the objective of our study was to analyze the disparate methods used to assess AAI and its normal range and to recommend a standardized method to assess AAI based on that analysis. We made an inventory of the disparate AAI methods and its normal range reported in 100 randomly selected publications and recommend the means of such standardization. We recommend that an experienced observer assess AAI with the patient at rest in the supine position. The width of the sphygmometer cuffs should be 1.5 times that of the extremity to be measured, and brachial and crural pulses should be detected using a Doppler device. Systolic pressures should be measured at both arms and over the anterior and posterior arteries of both legs, with the cuff placed just proximally to the malleoli. The left arm pressure ought to be used as denominator and the mean of pressures of both crural arteries of each leg ought to be used for the numerator of the AAI for that leg. We advocate 0.90 as the cut-off value to distinguish patients who need further arterial assessment.
Diagnostic utility of the two methods of ankle brachial index in the detection of peripheral arterial disease of lower extremities.
Niazi K, Khan TH, Easley KA. Catheter Cardiovasc Interv. 2006 Oct 12;68(5):788-792
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BACKGROUND:: Peripheral arterial disease (PAD) is a common disease that is diagnosed with a screening test called the Ankle Brachial Index (ABI). Different methods of ABI have been described in the literature. We wanted to estimate and compare the sensitivity and specificity of an alternative method of calculating the ABI (LAP ABI, low ankle pressure ABI) with the current method (named high ankle pressure (HAP)), using digital subtraction angiography (DSA) as the gold standard.
METHODS:: We reviewed the records of all patients who had undergone DSA at a major academic center between August 2003 and October 2005.The study includes 107 patients/208 limbs. Inclusion criteria included patients with an ABI performed within 30 days prior to the DSA. Patients with noncompressible vessels and ABI >1.40 were excluded. Abnormal ABI was defined as </=0.9 for both methods. Disease on angiogram was defined as the presence of 50% or more stenosis of any lower extremity artery from the aorto-illiac bifurcation to the ankle arteries.
RESULTS:: The sensitivity of the HAP and LAP ABI for the diagnosis of PAD was 69 and 84%, respectively (P < 0.001). The specificity of the HAP and the LAP method was 83 and 64% respectively (P < 0.01). The overall accuracy of LAP ABI and HAP ABI was 80 and 72%, respectively.
CONCLUSIONS:: The LAP ABI has better sensitivity and overall accuracy in comparison to the HAP ABI to diagnose PAD
Reproducibility and reliability of the ankle-brachial index as assessed by vascular experts, family physicians and nurses.
Holland-Letza T, Endres HG, Biedermann S, Mahn M, Kunert J, Groh S, Pittrow D, von Bilderling P, Sternitzky R, Diehm C. Vasc Med. 2007 May;12(2):105-12.
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The reliability of ankle-brachial index (ABI) measurements performed by different observer groups in primary care has not yet been determined. The aims of the study were to provide precise estimates for all effects influencing the variability of the ABI (patients' individual variability, intra- and inter-observer variability), with particular focus on the performance of different observer groups. Using a partially balanced incomplete block design, 144 unselected individuals aged > or = 65 years underwent double ABI measurements by one vascular surgeon or vascular physician, one family physician and one nurse with training in Doppler sonography. Three groups comprising a total of 108 individuals were analyzed (only two with ABI < 0.90). Errors for two repeated measurements for all three observer groups did not differ (experts 8.5%, family physicians 7.7%, and nurses 7.5%, p = 0.39). There was no relevant bias among observer groups. Intra-observer variability expressed as standard deviation divided by the mean was 8%, and inter-observer variability was 9%. In conclusion, reproducibility of the ABI measurement was good in this cohort of elderly patients who almost all had values in the normal range. The mean error of 8-9% within or between observers is smaller than with established screening measures. Since there were no differences among observers with different training backgrounds, our study confirms the appropriateness of ABI assessment for screening peripheral arterial disease (PAD) and generalized atherosclerosis in the primary case setting. Given the importance of the early detection and management of PAD, this diagnostic tool should be used routinely as a standard for PAD screening. Additional studies will be required to confirm our observations in patients with PAD of various severities.
Prognostic significance of declining ankle-brachial index values in patients with suspected or known peripheral arterial disease.
Feringa HH, Karagiannis SE, Schouten O, Vidakovic R, van Waning VH, Boersma E, Welten G, Bax JJ, Poldermans D. Eur J Vasc Endovasc Surg. 2007 Aug;34(2):206-13.
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BACKGROUND: Peripheral arterial disease (PAD) is a risk factor for cardiovascular events. This study assessed the prognostic significance of repeated ankle-brachial index (ABI) measurements at rest and after exercise in patients with PAD receiving conservative treatment.
METHODS: In a cohort study of 606 patients (mean age 62+/-12 years, 68% male), ABI at rest and after exercise was measured at baseline and after 1 year. Patients with reductions in ABI were divided into three equally-sized groups (minor, intermediate and major reductions) and were compared to patients without reductions. During a mean follow-up of 5+/-3 years, all-cause mortality, cardiac events, stroke and progression to kidney failure were noted.
RESULTS: Death was recorded in 83 patients (14%) of which 49% were due to cardiac causes. Non-fatal myocardial infarction occurred in 38 patients (6%), stroke in 46 (8%) and progression to kidney failure in 35 (6%). By multivariate analysis, patients with major declines in resting (>20%) and post-exercise (>30%) ABI were at increased risk of all-cause mortality (HR: 3.3, 95% CI: 1.5-7.2, HR: 3.0, 95% CI: 1.4-6.4, respectively), cardiac events (HR: 3.1, 95% CI: 1.3-7.2, HR: 2.4, 95% CI: 1.1-5.6, respectively), stroke (HR: 4.2, 95% CI: 1.6-10.4, HR: 3.9, 95% CI: 1.4-10.2, respectively) and kidney failure (HR: 2.7, 95% CI: 1.1-7.5, HR: 6.9, 95% CI: 1.5-31.5, respectively), compared to patients with no declines in ABI.
CONCLUSIONS: This study shows that major 1-year declines in resting and post-exercise ABI are associated with all-cause mortality, cardiac events, stroke and kidney failure in patients with PAD
Gosh, look how many articles!!! I reckon ABI's are a great screening tool to ascertain whether further testing needs to be done - but not to be used on their own - signs and symptoms and presence of pulses are essential. I think the great thing about the promotion of ABI's is that practitioners will actually think to look down at the feet!
Ankle-brachial pressure index estimated by laser Doppler in patients suffering from peripheral arterial obstructive disease.
Ludyga T, Kuczmik WB, Kazibudzki M, Nowakowski P, Orawczyk T, Glanowski M, Kucharzewski M, Ziaja D, Szaniewski K, Ziaja K. Ann Vasc Surg. 2007 Jul;21(4):452-7.
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Ankle-brachial index (ABI) measurements are widely used for evaluating the functional state of circulation in the lower limbs. However, there is some evidence that the value of ABI does not accurately reflect the degree of walking impairment in symptomatic patients with peripheral arterial obstructive disease (PAOD). We investigated the diagnostic value of ABI estimated by means of laser Doppler flowmetry (IT) for evaluating limb ischemia. We wanted to know whether laser Doppler could be more sensitive than the Doppler method in predicting walking capacity in patients with stable intermittent claudication. We analyzed a group of 30 patients with intermittent claudication (Fontain II, II/III) who were admitted for reconstructive treatment. There were 21 men and 9 women, aged 46-74 (mean 61) years. All patients underwent the treadmill test, and pain-free walking distances were measured. In each patient, we measured ABI using the two different methods: Doppler ultrasound device (ABI-Doppler) and laser Doppler (ABI-laser Doppler). The claudication distances were 25-200 m (mean 73 +/- 50.2 m). ABI-Doppler was 0.2-0.7 (0.582 +/- 0.195). ABI-laser Doppler measurements were 0.581 (+/-0.218). A correlation was found between ABI-Doppler and claudication distance (r = 0.46, P = 0.009). Also, ABI-laser Doppler values significantly correlated with claudication distances (r = 0.536, P = 0.002). The ABI evaluated by laser Doppler correlated well with claudication distances in patients with PAOD. Comparison of Doppler and laser Doppler measurements used for determining ABI showed that both methods have similar predictive power for walking capacity; however, higher correlation was observed between claudication distances and ABI measured by laser Doppler flowmetry. ABI-laser Doppler measurements are easier, are quicker, and seem to be better suited for noncompliant patients. Further investigation should be undertaken to determine whether laser Doppler is superior to the Doppler method in advanced occlusive arterial disease.
Preliminary study to investigate the normal range of Ankle Brachial Pressure Index in young adults.
Male S, Coull A, Murphy-Black T. J Clin Nurs. 2007 Oct;16(10):1878-85.
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AIM: The aim of this study was to find the normal range of Ankle Brachial Pressure Index (ABPI) for healthy adults in the 20-40-year age group. The hypothesis was: there is no difference between the accepted normal value of ABPI (1.00) and the observed value of ABPI in healthy adults in the 20-40-year age group.
BACKGROUND: Doppler ultrasound and ABPI calculations are used in the assessment of lower limb vascularity. Ankle Brachial Pressure Index is used as an indicator for the choice of nursing options for the treatment of chronic leg ulcers. Little research has been done to establish what the normal range of ABPI is in young healthy adults. This information has practical significance to the treatment of young adults who are prone to present with leg ulcers such as i.v. drug users.
METHOD: An observational survey was conducted with 24 healthy adults in the 20-40-year age range (who did not have a history of i.v. drug use).
RESULTS: The study found that the ABPI ranged from 1.05 to 1.25 (mean = 1.14; SD 0.06). In addition, the study also found that there was a negative correlation between ABPI and observed brachial systolic pressure.
CONCLUSION: A 'normal' ABPI should not be considered a fixed figure (1.00) and that ABPI may be dependant on an individual's blood pressure and possibly other factors.
RELEVANCE TO CLINICAL PRACTICE. Ankle Brachial Pressure Index is a routine procedure undertaken when assessing the vascular supply to the lower legs. The results summarized in this paper will be useful to clinicians attempting to interpret ABPI results in young people
Ankle brachial index measurement in primary care: are we doing it right?
Nicolaï SP, Kruidenier LM, Rouwet EV, Bartelink ML, Prins MH, Teijink JA. Br J Gen Pract. 2009 Jun;59(563):422-7.
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BACKGROUND: The reference standard for diagnosing peripheral arterial disease in primary care is the ankle brachial index (ABI). Various methods to measure ankle and brachial blood pressures and to calculate the index are described. AIM: To compare the ABI measurements performed in primary care with those performed in the vascular laboratory. Furthermore, an inventory was made of methods used to determine the ABI in primary care.
DESIGN OF STUDY: Cross-sectional study. SETTING: Primary care practice and outpatient clinic. METHOD: Consecutive patients suspected of peripheral arterial disease based on ABI assessment in primary care practices were included. The ABI measurements were repeated in the vascular laboratory. Referring GPs were interviewed about method of measurement and calculation of the index. From each patient the leg with the lower ABI was used for analysis.
RESULTS: Ninety-nine patients of 45 primary care practices with a mean ABI of 0.80 (standard deviation [SD] = 0.27) were included. The mean ABI as measured in the vascular laboratory was 0.82 (SD = 0.26). A Bland-Altman plot demonstrated great variability between ABI measurements in primary care practice and the vascular laboratory. Both method of blood pressure measurements and method of calculating the ABI differed greatly between primary care practices.
CONCLUSION: This study demonstrates that the ABI is often not correctly determined in primary care practice. This phenomenon seems to be due to inaccurate methods for both blood pressure measurements and calculation of the index. A guideline for determining the ABI with a hand-held Doppler, and a training programme seem necessary.
Interobserver variability of ankle-brachial index measurements at rest and post exercise in patients with intermittent claudication.
van Langen H, van Gurp J, Rubbens L. Vasc Med. 2009 Aug;14(3):221-6.
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The ankle-brachial index (ABI) post exercise is claimed to play a complementary role in the diagnosis or exclusion of intermittent claudication (IC). The interobserver variability of ABI measurements at rest and post exercise in patients with typical symptoms of IC is the subject of this study with emphasis on ABI post exercise. ABI at rest and post exercise were measured in both legs of 20 patients with typical symptoms of IC. After 15 minutes of rest these measurements were repeated by another observer. Analysis according to Bland-Altman was performed on 40 paired leg measurements at rest and 40 paired leg measurements post exercise. The average ABI at rest for the first observer was 0.84 (standard deviation +/-0.18) and for the second was 0.84 (+/-0.17). Post-exercise averages were 0.73 (+/-0.25) and 0.74 (+/-0.27), respectively. The standard deviation of the ABI difference between observers was 0.08 at rest and 0.15 post exercise. The interobserver variability of the ABI was 10% at rest and 21% post exercise. The interobserver variability post exercise is an important given when rules are defined about how the ABI post exercise translates into a more reliable and objective diagnosis of IC.
Comparison of ankle-brachial index measured by an automated oscillometric apparatus with that by standard Doppler technique in vascular patients.
Kornø M, Eldrup N, Sillesen H. Eur J Vasc Endovasc Surg. 2009 Nov;38(5):610-5.
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OBJECTIVES: To evaluate the determination of ankle-brachial indices (ABIs) using a simple automated ankle pressure measurement device in comparison with the Doppler technique. DESIGN: ABI was measured in 61 patients (122 legs) admitted to the department of vascular surgery, Rigshospitalet. ABI was calculated twice using both the methods on both legs.
MATERIALS AND METHODS: We tested the automated oscillometric blood pressure device, CASMED 740, for measuring ankle and arm blood pressure and compared it with the current gold standard, the hand-held Doppler technique, by the Bland-Altman analysis.
RESULTS: Using the Doppler-derived ABI as the gold standard, the sensitivity and specificity of the oscillometric method for determining an ABI<or=0.9 is 71% and 92%, respectively. The overall accuracy for correctly identifying an ABI of 0.9 with the oscillometric method was 82%. Ankle pressures measured by CASMED 740 were systematically higher in patients with reduced ankle pressures, but accurate in patients with ankle pressures above 90 mm Hg.
CONCLUSION: Automated oscillometric assessment of ankle blood pressure and ABI may falsely categorise PAD patients as having a normal ankle pressure and ABI
Reliability of the ABI
Linear Mode
