Validation of arteriovenous access stage (AVAS) classification: a prospective, international multicentre study

Area of Science:

• Nephrology
• Vascular Surgery
• Medical Imaging

Background:

• The Arteriovenous Access Stage (AVAS) classification system categorizes upper extremity vessels for vascular access (VA) suitability.
• It classifies patients into three groups: AVAS1 (native fistula), AVAS2 (prosthetic graft), and AVAS3 (unsuitable for conventional VA).

Purpose of the Study:

• To prospectively validate the effectiveness of the AVAS classification system in predicting vascular access creation and outcomes.
• To assess the accuracy and consistency of AVAS assessments among evaluators.

Main Methods:

• A prospective, international observational study (NCT04796558) enrolled 1034 patients across 11 centers.
• Data collected included demographics, risk factors, vessel parameters, VA types, AVAS class, and early VA failure.
• Evaluated AVAS predictive ability and inter-evaluator consistency using percentage agreement; compared early failure rates using Pearson's Chi-squared test.

Main Results:

• The AVAS distribution was AVAS1 (91.2%), AVAS2 (7.2%), and AVAS3 (1.6%). Inter-evaluator agreement was 89%.
• The accuracy of AVAS prediction versus created access was 79%, outperforming clinician prediction (62.1%).
• Unconventional VA had a higher early failure rate (20%) than conventional VA (9.3%, P=.002).

Conclusions:

• AVAS is effective in predicting VA creation, though accuracy diminishes in higher classes due to complex decision-making and vessel preservation needs.
• Following AVAS guidelines significantly decreased early vascular access failure rates.