Cost-Effectiveness of Focused Ultrasound vs AV Duplex Scan
Based on current evidence, focused ultrasound (duplex ultrasound) is NOT cheaper than AV duplex scan—they are the same modality. The question appears to conflate terminology, as "focused ultrasound" in vascular imaging typically refers to duplex ultrasound (DUS), which combines B-mode imaging with Doppler flow assessment and is the standard modality for arteriovenous (AV) access evaluation 1.
Clarification of Terminology
Duplex ultrasound (DUS) is the cost-effective first-line imaging modality for peripheral vascular disease assessment, including AV fistula surveillance, combining anatomical visualization with hemodynamic flow information 1.
The term "focused ultrasound" in medical imaging generally refers to either point-of-care ultrasound examinations or therapeutic high-intensity focused ultrasound (HIFU), not a distinct diagnostic modality from duplex scanning 1.
Cost-Effectiveness Evidence for Duplex Ultrasound
Comparative Cost Analysis
Duplex ultrasound is significantly more cost-effective than cross-sectional imaging (CT angiography or MR angiography) for vascular surveillance, with both MRA and CTA being more cost-effective than duplex US for preoperative planning, but duplex remaining the most economical option for routine surveillance 1.
In EVAR surveillance, duplex-based strategies generate lower expected costs and higher quality-adjusted life-years (QALYs) than CTA-based strategies, with a 63% probability of being cost-effective at a £30,000 willingness-to-pay-per-QALY threshold 2.
Cost savings of $1,595 per patient per year were realized by using duplex ultrasound as the sole surveillance modality instead of serial CT scans in post-EVAR patients, with a 29% reduction in total surveillance costs 3.
Limitations Affecting Cost-Effectiveness
Duplex ultrasound requires highly skilled sonographers and can require over an hour to perform, making it operator-dependent and time-consuming, which impacts overall cost-effectiveness in some clinical settings 1.
In many centers, diagnostic confidence with duplex ultrasound is low for preoperative arterial mapping, and additional studies are often ordered, rendering duplex arterial preoperative mapping a less cost-effective option because further studies are frequently required 1.
Duplex ultrasound has limited utility for evaluating tibial arteries for distal bypass or choosing specific treatment plans with high confidence, necessitating supplementary imaging in complex cases 1.
Clinical Performance Considerations
Accuracy and Sensitivity
Duplex ultrasound has 88-90% sensitivity and 95-98% specificity for detecting >50% stenosis in peripheral arteries from the iliac to popliteal level 1.
For AV fistula surveillance, novel Doppler ultrasound devices demonstrate strong correlation (r = 0.781, p < 0.001) with traditional duplex ultrasound for volume flow rate measurements, with moderate to good agreement (ICC = 0.750) 4.
Duplex ultrasound detected all clinically significant endoleaks in EVAR surveillance with 86% sensitivity and 94% negative predictive value, though specificity was only 67% due to false positives 5.
Technical Limitations
Accuracy is diminished when bowel gas or tortuosity obscures iliac vessels, and dense calcification can obscure flow, particularly when flow is slow 1.
Adequate visualization is not possible in 1.7% of patients, predominantly due to obesity, limiting universal applicability 5.
Duplex ultrasound accuracy decreases in the setting of multiple sequential lesions, requiring careful interpretation and potentially supplementary imaging 1.
Practical Cost-Effectiveness Algorithm
When Duplex Ultrasound Alone Is Cost-Effective:
- Routine surveillance of AV fistulas for hemodialysis, where volume flow rate trending is the primary objective 4
- Post-EVAR surveillance in non-obese patients without complex anatomy, reserving CTA for abnormal/inconclusive duplex findings 2, 3, 5
- Screening for peripheral arterial disease in patients aged ≥65 years with cardiovascular risk factors 1
- Follow-up after lower extremity angioplasty, particularly for femoropopliteal lesions where duplex has >80% concordance with angiography 1
When Additional Imaging Is Required (Reducing Cost-Effectiveness):
- Preoperative planning for complex revascularization, where cross-sectional imaging provides superior anatomical detail 1
- Evaluation of tibial and pedal arteries for distal bypass planning, where MRA or CTA is superior 1
- Patients with severe obesity or extensive calcification, where ultrasound penetration is inadequate 1, 5
- When duplex findings are inconclusive or discordant with clinical presentation, necessitating confirmatory CTA/MRA 1
Common Pitfalls to Avoid
Do not assume duplex ultrasound can replace cross-sectional imaging for all vascular applications—its cost-effectiveness is context-dependent and highest for surveillance rather than initial diagnostic workup 1.
Ensure adequate technical expertise is available—the operator-dependent nature of duplex ultrasound means that cost savings are only realized when skilled sonographers perform high-quality examinations without requiring repeat studies 1.
Recognize that low positive predictive value (45%) for endoleak detection means many positive duplex findings require CTA confirmation, potentially negating cost savings if not managed with appropriate clinical algorithms 5.