The accuracy of toe brachial index and ankle brachial index in the diagnosis of lower limb peripheral arterial disease: A systematic review and meta-analysis.

BACKGROUND AND AIMS: We aimed to compare the diagnostic accuracy of ankle brachial index (ABI) and toe brachial index (TBI) for peripheral arterial disease (PAD) in a wide spectrum of PAD populations and reference standard tests, and to examine variables influencing heterogeneity in the estimates. METHODS: Systematic searches in EMBASE, MEDLINE, Web of Science and the Cochrane Library databases were performed, from inception to January 2020. Hierarchical summary receiver operating characteristic curves (HSROC) were used to summarize the pooled test performance. RESULTS: Thirty five (patient-level: 1318 patients, limb-level: 5637 limbs) and nine studies (patient-level: 294 patients, limb-level: 826 limbs) were included in ABI and TBI meta-analyses, respectively. The QUADAS-2 tool identified many studies with high risk of bias, especially in the "patient selection" domain. Pooled estimates for ABI in detecting 50% or greater stenosis were sensitivity = 61% (95% CI: 55-69), specificity = 92% (95% CI: 89-95) and dOR = 16.5 (95% CI: 11.5-23.6). Similarly, TBI yielded sensitivity = 81% (95% CI: 70-94), specificity = 77% (95% CI: 66-90) and dOR = 13.1 (95% CI: 7.0-24.8). In a direct comparison of seven studies jointly analyzing ABI and TBI, TBI showed better overall diagnostic accuracy (16.4 vs 11.0 in dOR) at the expense of sensitivity (82% vs 52%), while specificity (77% vs 94%) performed worse in TBI than ABI. Heterogeneity was large in sensitivity for ABI, with variables as different reference standard tests, smoking habit and PAD prevalence accounting for such variability. Similarly, gender, different index test cut-offs and sample size influenced the heterogeneity in TBI specificity. CONCLUSIONS: Though ABI and TBI showed similar diagnostic performance to diagnose PAD, TBI showed far better sensitivity than ABI, especially in "challenging populations", as those exhibiting calcification.

Physical examination to screen for peripheral artery disease in a defined Primary Care population: A diagnostic accuracy study.

INTRODUCTION: Peripheral arterial disease (PAD) is an underdiagnosed prevalent disease which implies high cardiovascular risk. Professionals usually depend on physical examination to screen for PAD. OBJECTIVE: To assess the diagnostic accuracy of physical examination to screen for PAD in a rural Primary Care population and to evaluate the nurse-physician level of agreement in pedal pulse palpation. METHODS: Diagnostic accuracy study in which two experienced professionals (physician-nurse) prospectively performed pedal pulse palpation (grading as absent, reduced, normal, or bounding), femoral bruit auscultation and calf circumference (index tests) comparing with Doppler ABI (reference test, positive cut-off: 0.9 ≥ ABI ≥ 1.4) in 158 consecutive subjects. INCLUSION CRITERIA: presence of diabetes, dyslipidaemia, hypertension, smoking habit (current or former), or age ≥ 65. RESULTS: Of 315 legs included, PAD was confirmed in 38 (12.1%) legs. Absent dorsalis pedis (DP) and posterior tibial (PT) pulses were found in 37 (11.7%) and 67 (21.3%) legs, respectively. Regarding nurse evaluation, when a positive test was set if DP or PT were absent (more sensitive cut-off), sensitivity was = 86.8 (95% CI: 74.8-98.9), specificity = 82.7 (95% CI: 78.0-87.3), likelihood ratio+ = 5.01 (95% CI: 3.77-6.67), likelihood ratio- = 0.16 (95% CI: 0.07-0.36), and diagnostic odds ratio (dOR) = 31.5 (95% CI: 11.7-84.8). Age, diabetes, and calcification (ABI ≥ 1.4) influenced the rate of a false negative finding in pedal palpation. Physician-nurse weighted kappa coefficient was = 0.649 (95% CI: 0.599-0.699). The presence of a femoral bruit auscultation had a dOR = 3.8 (95% CI: 1.1-13.1), and a calf circumference <34.55 cm had a dOR = 3.2 (95% CI: 1.6-6.4). CONCLUSIONS AND RELEVANCE: In a mainly asymptomatic Primary Care population, pedal pulse palpation was by far the best diagnostic test, with good diagnostic accuracy and inter-rater agreement. In view of a high sensitivity and capacity to rule out the disease, pedal pulse palpation could be performed as a screening test for PAD and individuals at high cardiovascular risk.

Spectrum effect and spectrum bias in the oscillometric ankle brachial index to diagnose peripheral arterial disease: Clinical implications.

BACKGROUND AND AIMS: The diagnostic performance of the oscillometric ankle brachial index (ABI) to detect peripheral arterial disease (PAD) varies among populations, suggesting a spectrum effect. When this heterogeneity modifies post-test probabilities, a spectrum bias arises. This study evaluates the presence and influence of spectrum effect and spectrum bias on test performance and clinical decisions. METHODS: Oscillometric and Doppler ABI were compared in two settings: Primary-Care (333 legs) and Vascular-Service (41 legs). Spectrum effect was assessed using stratification and logistic regression, while spectrum bias was assessed through graphical and statistical tests based on predictive values and likelihood ratios, respectively. RESULTS: Across subgroups, sensitivity ranged from 61.5% to 90.9%, and specificity from 81.8% to 99.1%. Logistic regression confirmed a spectrum effect in setting, diabetes, smoking status and age (univariate), and setting and diabetes (multivariate model). The positive likelihood ratio ranged from 5.0 to 89.1 in subgroups, leading to a spectrum bias in diabetic, smoking (both subgroups) and age (both subgroups). Therefore, a positive test ruled in differently the disease across subgroups, with a high rate of false positives in diabetic, smoking and >75-year-old patients. The negative likelihood ratio ranged from 0.09 to 0.39 in subgroups, with significant spectrum bias in Primary-Care patients, non-diabetics and smokers. Thus, in these subgroups, a negative test ruled out the disease with less certainty. CONCLUSIONS: Spectrum effect and spectrum bias were found in oscillometric ABI to detect PAD, potentially affecting clinical decisions, especially for positive tests. Information about spectrum variables and the application of specific subgroups indicators are necessary.

Simultaneous inter-arm and inter-leg systolic blood pressure differences to diagnose peripheral artery disease: a diagnostic accuracy study.

PURPOSE: Inter-arm systolic blood pressure differences (IASBPD) and inter-leg systolic blood pressure differences (ILSBPD) have arisen as potential tools to detect peripheral artery disease (PAD) and individuals at high cardiovascular risk. This study aims to evaluate the diagnostic accuracy of IASBPD and ILSBPD to detect PAD, and whether IASBPD or ILSBPD improves diagnostic accuracy of the oscillometric ankle-brachial index (ABI). MATERIALS AND METHODS: In this prospective study, eligible for inclusion were consecutive adults, with at least one of the following cardiovascular risk factors: diabetes, dyslipidemia, hypertension, smoking habit or age ≥65. IASBPD, ILSBPD and ankle-brachial index (ABI) were measured in all participants through four-limb simultaneous oscillometric measurements and compared with Doppler ABI (reference test, positive cut-off: ≤ 0.9). RESULTS: Of 171 subjects included, PAD was confirmed in 23 and excluded in 148. Thirteen and 38 subjects had IASBPD and ILSBPD ≥10 mmHg, respectively. Pearson correlation with Doppler ABI of IASBPD and ILSBPD was 0.073 (P = .343) and -0.628 (P < .001), respectively. Diagnostic accuracy of an ILSBPD ≥10 mmHg to detect PAD was: sensitivity = 69.6% (95%CI = 48.6-90.5), specificity = 85.1% (79.1-91.2), diagnostic odds ratio (dOR) = 13.1 (4.8-35.5) and area under ROC curve (AUC) = 0.765 (0.616-0.915). IASBPD had an AUC = 0.532 (0.394-0.669), and oscillometric ABI had an AUC = 0.977 (0.950-1.000). The addition of ILSBPD to oscillometric ABI reduced dOR from 174.0 (38.3-789.9) to 34.4 (9.5-125.1). Similarly, the addition of IASBPD reduced dOR to 49.3 (14.6-167.0). CONCLUSIONS: In a Primary Care population with ≥1 cardiovascular risk factors, ILSBPD showed acceptable diagnostic accuracy for PAD, whilst IASBPD accuracy was negligible. However, the combination of ILSBPD (or IASBPD) with oscillometric ABI did not improve the ability to detect PAD. Thus, oscillometer ABI seems to be preferable to detect PAD and individuals at high cardiovascular risk. ILSBPD could be uniquely recommended for the diagnosis of PAD when blood pressure measurements in upper limbs are not possible.

Factors affecting the validity of the oscillometric Ankle Brachial Index to detect peripheral arterial disease.

BACKGROUND: The use of oscillometric Ankle Brachial Index (ABI) to diagnose peripheral arterial disease (PAD) has raised concern, especially due to a lack of agreement and sensitivity. This study aimed to evaluate those factors affecting the validity of oscillometric ABI in comparison to Doppler ABI to detect PAD. METHODS: Through univariate and multivariate linear regression, we studied those factors affecting the differences between oscillometric and Doppler ABI; through univariate and multivariate logistic regression we analyzed the false negative rate of oscillometric ABI to detect PAD. RESULTS: We analyzed 197 consecutive subjects (394 legs) from two settings: Primary Care and Vascular Service. The means of oscillometric ABI and Doppler ABI were 1.094 (95% CI: 0.843-1.345) and 1.073 (95% CI: 0.769-1.374) (P<0.001), respectively. In men, covariates explaining the differences between oscillometric and Doppler ABI were Doppler ankle blood pressure (ß=-0.610, P<0.001), ankle circumference (ß=0.176, P=0.004) and oscillometric brachial blood pressure (ß=0.136, P=0.037); in women, those were weight (ß=0.351, P<0.001) and Doppler ankle blood pressure (ß=-0.318, P<0.001). Sensitivity and specificity of oscillometric ABI to detect PAD were 80.6% and 97.4%, respectively, and covariates explaining the rate of false negatives in PAD population were setting (Exp(ß)=17.21, P=0.009) and tobacco (packs/year) (Exp(ß)=1.049, P=0.002). CONCLUSIONS: Although some factors influencing the lack of agreement between oscillometric and Doppler ABI were identified, the correction of oscillometric ABI seems impractical, since Doppler is needed, the bias is not always uniformly distributed and its clinical relevance is small. According to sensitivity, borderline oscillometric ABI in Primary Care settings and smokers suggest PAD.