European Journal of Cardiovascular Medicine

Diabetes mellitus is a chronic metabolic disorder associated with a wide range of microvascular and macrovascular complications. [1] Among these, peripheral vascular disease (PVD) is a significant cause of morbidity, particularly in patients with diabetic foot ulcers (DFUs). [2] DFUs result from a combination of neuropathy, immunosuppression, and vascular insufficiency. PVD in diabetic patients tends to be more extensive and diffuse, often involving distal arteries and leading to critical limb ischemia, non-healing ulcers, infections, and eventually, limb loss. [3] It has been estimated that diabetes accounts for nearly 50% of non-traumatic lower limb amputations, with DFU frequently preceding these events. [1]

The early identification of PVD in diabetic individuals with foot ulcers is crucial in improving outcomes. However, clinical examination alone is often inadequate due to the high prevalence of asymptomatic PVD in diabetics. Various diagnostic tools are available for evaluating lower limb perfusion. [4] Among these, the Ankle-Brachial Pressure Index (ABPI) is widely used due to its simplicity, non-invasiveness, and cost-effectiveness. ABPI is calculated as the ratio of systolic blood pressure at the ankle to that at the brachial artery. [5] An ABPI value below 0.90 is generally indicative of PVD. [5] Nonetheless, its reliability in diabetic populations is challenged by arterial wall calcification, which can result in falsely elevated readings.

Color doppler ultrasonography (CDU), a combination of B-mode imaging and spectral Doppler, provides anatomical and hemodynamic information about blood flow in the lower limb arteries. It allows for localization of stenosis or occlusion and is considered a standard non-invasive modality for the diagnosis of PVD. [1] Despite its superior diagnostic utility, CDU is more resource-intensive and operator-dependent, which may limit its use in primary healthcare settings or resource-limited regions.

In clinical practice, especially in developing countries like India, it is essential to identify a screening test that balances diagnostic accuracy with feasibility. This study was undertaken to compare the diagnostic performance of ABPI against CDU in detecting PVD in patients with DFU. The aim was to assess whether ABPI could serve as a reliable screening tool in resource-constrained settings, thereby aiding in the timely management and prevention of complications associated with diabetic foot disease.

This prospective comparative study was conducted in the Department of General Surgery at Mamata Medical College and General Hospital, Khammam, Telangana, over a period of two years from August 2022 to July 2024. A total of 100 adult patients diagnosed with diabetic foot ulcers and admitted to the general surgery wards were enrolled consecutively. The inclusion criteria consisted of patients aged 18 years or older with clinically diagnosed diabetic foot ulcers who provided informed consent to participate. Patients were excluded if they had rest pain, signs suggestive of critical limb ischemia, other identifiable causes of peripheral neuropathy, were under 18 years of age, or declined to participate.

After obtaining approval from the Institutional Ethics Committee, informed consent was taken from all participants. Each patient underwent a detailed clinical history and physical examination, including evaluation of peripheral pulses and signs of limb ischemia. Laboratory investigations included fasting blood glucose, glycosylated hemoglobin (HbA1c), lipid profile, renal function tests, and wound culture where appropriate.

ABPI was measured using a handheld Doppler device (EMCO®) by calculating the ratio of the highest ankle systolic pressure (from dorsalis pedis or posterior tibial artery) to the highest brachial systolic pressure. A value <0.90 was considered diagnostic for PVD. Subsequently, all patients underwent color duplex ultrasonography of both lower limbs, performed by a trained radiologist, to assess the presence and degree of arterial obstruction. An obstruction >50% on CDU was considered significant for PVD.

Management of DFU was based on standard institutional protocols and included glycemic control, wound care, debridement, appropriate antibiotic therapy guided by culture and sensitivity, and surgical interventions such as skin grafting or amputation when indicated.

All data were entered into Microsoft Excel and analyzed using SPSS version 23. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of ABPI were calculated using CDU as the reference standard. Chi-square test was used for categorical variables, and a p-value <0.05 was considered statistically significant.

This study enrolled 100 patients diagnosed with diabetic foot ulcers. The mean age of the study population was 56.4 ± 11.67 years and male-to-female ratio was 3:1 (Table 1). The mean duration of DM was 6.9 ± 3.17 years, and 72% of participants had been diagnosed for more than five years. Common associated factors included smoking (52%), alcohol consumption (48%), walking barefoot (42%), and a prior history of ulceration or amputation (36%). Hypertension (56%) and dyslipidemia (58%) were the most prevalent comorbidities.

Table 1: Distribution of subjects according to age and gender

In terms of treatment, 32% of patients were on oral hypoglycemic agents (OHA) alone, 12% on insulin alone, and the majority (56%) were on a combination of both. The mean fasting blood sugar was 171.5 ± 65.22 mg/dL, and the mean HbA1c was 8.9 ± 2.48%.

Regarding the ABPI, 78% of patients had abnormal values (<1.0), indicative of PVD, while only 22% had values within the normal range (≥1.0) (Figure 1). On color duplex ultrasonography, 70 patients (70%) showed significant arterial obstruction (>50%). The most commonly involved arteries were the anterior and posterior tibial arteries (involved simultaneously in 31.4% of cases), followed by isolated anterior tibial (25.8%) and posterior tibial (11.1%) arteries.

Table 2: Distribution of subjects according to ABPI vs colour Doppler ultrasound

A comparative diagnostic analysis revealed that ABPI correctly identified PVD in 68 out of the 70 patients diagnosed with PVD by CDU. However, ABPI failed to detect PVD in 2 patients who were positive on CDU. Conversely, 10 patients with abnormal ABPI were found to have normal duplex scans (Table 2). This yielded a sensitivity of 97.14%, specificity of 66.67%, positive predictive value of 87.18%, and negative predictive value of 90.91%. A total of 32 patients (32%) required amputations; of these, 20 underwent minor amputations (e.g., ray’s amputation), while 12 required major limb amputations.

Figure 1: Pie chart showing distribution according to ABPI

The ABPI, defined as the ratio of systolic blood pressure at the ankle to that at the brachial artery, was originally developed as a non-invasive diagnostic tool for lower-extremity PAD. Beyond its diagnostic utility, ABPI has also been recognized as a prognostic marker for systemic atherosclerosis and cardiovascular risk, even in asymptomatic individuals.

DM is associated with both microvascular and macrovascular complications, with foot ulcers being a common manifestation due to neuropathy and peripheral vascular disease. Up to 50% of non-traumatic lower limb amputations are attributable to diabetes, and early recognition of ischemia is essential to prevent limb loss. PVD, whether degenerative or vasospastic, is highly prevalent in this population and often underdiagnosed. Prompt, accessible, and cost-effective tools like ABPI are therefore indispensable, especially in primary care settings.

In the current study, ABPI demonstrated a high sensitivity (97.14%) and moderate specificity (66.67%) compared to duplex ultrasound, reinforcing its role as a reliable screening modality. Similar results were observed by Agarwal et al. ^[1] and Weragoda et al., ^[5] affirming that while ABPI is excellent for detecting disease, confirmatory imaging remains necessary in ambiguous cases.

Baseline characteristics such as age, gender distribution, comorbid conditions, and risk factors in our cohort were comparable to several earlier studies conducted by Agarwal et al., ^[1] Weragoda et al., ^[5] Thomas et al., ^[6] and Premalatha et al. ^[7]   Most subjects were middle-aged males with long-standing diabetes and multiple cardiovascular risk factors.

Clinically, over two-thirds of the patients had ABPI values suggestive of PVD, and 70% had significant arterial obstruction on duplex scans. The most common arterial involvement included the anterior and posterior tibial arteries. These findings align with prior research, including studies by Thomas et al., ^[6] and Premalatha et al. ^[7], that showed high involvement of distal arteries in diabetic patients.

Laboratory profiles, including elevated fasting blood sugars and HbA1c levels, indicated poor glycemic control, consistent with the disease burden. Therapeutically, most patients were managed with combined OHA and insulin regimens, as reported in comparable diabetic foot cohorts.

The need for amputation was observed in 32% of patients, comparable to the 34% rate noted by Agarwal et al. ^[1] Notably, timely screening using ABPI could reduce such outcomes through earlier intervention.

Overall, our findings affirm that ABPI remains a valuable, non-invasive first-line diagnostic tool for PVD in diabetic patients, especially in resource-limited settings, while duplex ultrasound serves as a confirmatory and planning modality.

The findings of this study support the use of ABPI as a sensitive and accessible screening tool for peripheral vascular disease in patients with diabetic foot ulcers. Despite limitations in specificity, its high sensitivity and negative predictive value render it effective for ruling out significant PVD, especially in resource-constrained settings. Duplex ultrasound should be reserved for patients with abnormal ABPI results or those requiring detailed vascular mapping for surgical planning. Early screening with ABPI could potentially reduce morbidity, improve outcomes, and lower the incidence of major amputations among diabetic patients.

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