The Global Limb Anatomic Staging System (GLASS) for CLTI: Improving Inter-Observer Agreement

Area of Science:

• Vascular Surgery
• Interventional Cardiology
• Radiology

Background:

• Chronic Limb-Threatening Ischemia (CLTI) requires evidence-based revascularization strategies.
• The Global Vascular Guidelines introduced the Global Limb Anatomic Staging System (GLASS) to predict revascularization success.
• GLASS assesses atherosclerotic lesions in femoropopliteal and infrapopliteal segments.

Purpose of the Study:

• To evaluate the preliminary feasibility and observer variability of the GLASS.
• To assess the inter-observer agreement of the GLASS scoring system in CLTI patients.
• To determine if a refined scoring approach can improve GLASS reliability.

Main Methods:

• GLASS scoring was applied to femoropopliteal (FP) and infrapopliteal (IP) segments based on stenosis, length, and calcification.
• A stepwise approach involved three steps using different datasets and observer numbers.
• Inter-observer agreement was measured using Cohen's Kappa, with observers blinded to outcomes.

Main Results:

• Initial steps showed low inter-observer agreement (Kappa values 0.180-0.406).
• Refinement in step 3, including component scoring (calcification) and imaging aids (ruler), significantly improved agreement.
• Step 3 achieved higher Kappa values: 0.796 for FP and 0.730 for IP segments.

Conclusions:

• Unconditioned GLASS scoring demonstrated poor inter-observer agreement in this retrospective study.
• A stepwise component scoring method for GLASS provides acceptable agreement.
• This refined approach offers a foundation for prospective studies validating GLASS against treatment outcomes.