Central Vein stEnosis screeNing using Ultrasound guided Sniff test: A prospective diagnostic accuracy study (C-VENUS)

Abstract

Background:

Central venous stenosis (CVS) is a clinically significant complication in patients who depend on long-term hemodialysis access. While digital subtraction angiography remains the diagnostic gold standard, it is invasive, costly, and exposes patients to contrast and radiation. This study examined the diagnostic value of a simple, non-invasive, radiation-free alternative—the ultrasound-guided “sniff test,” which assesses dynamic changes in subclavian vein diameter during a forceful sniff to screen for CVS. Despite its potential advantages, the diagnostic performance of this method has not been well established.

Method:

A prospective study was conducted among 71 end-stage kidney disease (ESKD) patients scheduled for angiography. Each participant underwent a sniff test before the procedure. A reduction of more than 40% in subclavian vein diameter during sniffing was considered normal, indicating absence of stenosis. Angiographic findings were used as the reference standard. Clinical signs—specifically ipsilateral arm swelling and visible chest wall veins—were also evaluated for diagnostic utility.

Results:

Angiography confirmed CVS in 32 patients (45.1%). The sniff test showed a strong association with stenosis (OR 20.9) and demonstrated solid diagnostic performance, with sensitivity of 84.4%, specificity of 79.5%, and an AUC of 0.82. A normal sniff test accurately excluded stenosis in the majority of patients without CVS (86.1%), whereas an abnormal result was predominantly seen among those with stenosis (77.1%). Arm swelling was also significantly associated with stenosis (OR 20.40) and showed good standalone diagnostic accuracy (sensitivity 75.0%, specificity 87.2%, AUC 0.81). Importantly, combining the sniff test with clinical assessment enhanced overall performance, achieving higher specificity (94.9%) and excellent discriminative ability (AUC 0.90).

Conclusion:

In conclusion, the ultrasound sniff test is a promising, accessible, and accurate screening tool for CVS. Used alone or alongside clinical findings, it offers a practical method to identify patients who may benefit from confirmatory angiography—particularly valuable in resource-limited or radiation-averse settings.