CENTRAL VENOUS STENOSIS SCREENING USING ULTRASOUND GUIDED SNIFF TEST IN END-STAGE KIDNEY DISEASE PATIENTS: A PROSPECTIVE DIAGNOSTIC ACCURACY STUDY (C-VENUS)

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Abstract Title *

CENTRAL VENOUS STENOSIS SCREENING USING ULTRASOUND GUIDED SNIFF TEST IN END-STAGE KIDNEY DISEASE PATIENTS: A PROSPECTIVE DIAGNOSTIC ACCURACY STUDY (C-VENUS)

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Co-author 1

Jeevitha Brama Kumar jeevitha@ummc.edu.my Faculty of Medicine, University Malaya Department of Biomedical Imaging Kuala Lumpur Malaysia -

Co-author 2

Prasath Swaminathan prasath@ummc.edu.my Faculty of Medicine, University Malaya Department of Biomedical Imaging Kuala Lumpur Malaysia -

Co-author 3

Mohamad Zulfikrie Abas zulfikrie@moh.gov.my National Institutes of Health Malaysia Institute For Clinical Research Kuala Lumpur Malaysia -

Co-author 4

Kin Wong Chan kwchan@ummc.edu.my University Malaya Medical Centre Department of Biomedical Imaging Kuala Lumpur Malaysia -

Co-author 5

Ahmad Rafizi Hariz Ramli rafizihariz@ummc.edu.my Faculty of Medicine, University Malaya Vascular Unit, Division of General Surgery, Department of Surgery Kuala Lumpur Malaysia -

Co-author 6

Chye Chung Gan ccgan@ummc.edu.my Faculty of Medicine, University Malaya Division of Nephrology, Department of Medicine Kuala Lumpur Malaysia *

Co-author 7

Co-author 8

Co-author 9

Co-author 10

Co-author 11

Co-author 12

Co-author 13

Co-author 14

Co-author 15

Introduction

Central venous stenosis is a common complication in long-term hemodialysis patients. While digital subtraction angiography is the gold standard for diagnosis, it is resource-heavy, involves contrast administration, and radiation exposure. Ultrasound "sniff test" offers a novel non-invasive alternative for screening, though its diagnostic accuracy needs further investigation.

Methods

This prospective study involved patients from vascular and nephrology clinics scheduled for angiography due to suspected central venous stenosis (Diagram 1). Before the procedure, participants underwent an ultrasound sniff test, with an abnormal sniff result defined as <40% reduction in subclavian vein diameter during sniffing compared to at rest (Figure 1: Normal Sniff Test A & B, Abnormal Sniff Test D & E). Central venous stenosis was confirmed through angiographic findings, aiming to evaluate the diagnostic performance of the sniff test in detecting stenosis (Figure 1: Normal venogram C and Abnormal Venogram F).

Diagram 1: Flow of participants throughout study

Results

A total of 71 end-stage kidney disease patients were enrolled, with a median age of 67 years (IQR: 56, 75). Among them, 32 (45.1%) patients had confirmed stenosis and 39 (54.9%) did not (Table 1). An abnormal sniff test was strongly associated with stenosis (OR=20.9, 95% CI [6.1, 71.6], p<0.01), (Table 2). The test demonstrated high diagnostic performance: sensitivity 84.38%, 95% CI [67.21, 94.72]; specificity 79.49%, 95% CI [63.54, 90.70]; and an AUC of 0.82, indicating good accuracy. The positive predictive value was 77.14%, negative predictive value was 86.11%, and overall diagnostic accuracy was 81.69% (Table 3 and 4). A normal sniff test was common in patients without stenosis (86.1%), while an abnormal result was predominantly found in those with stenosis (77.1%).

Baseline characteristics Logistic regression of the sniff test against stenosis (cut-off 0.4) Table 3 Comprehensive diagnostic test using key performance indicators.png Figure 2: A. AUC for different sniff test cutoff. A 40% cutoff for sniff tests indicates the highest under the area ROC value; indicating 40% collapsability as significant. B. Area under the ROC curve was 0.82, indicating good discriminatory ability between patients with and without stenosis

Conclusion

The novel ultrasound-based sniff test demonstrates promising diagnostic performance in screening for central venous stenosis in end-stage kidney disease patients on long-term hemodialysis, with high sensitivity, specificity, and overall accuracy. Given its non-invasive nature and accessibility, it may serve as a useful preliminary tool for identifying patients requiring further confirmatory imaging via angiography, particularly in resource-limited settings.

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