Impact of Optical Coherence Tomography Angiography Scan Protocols on Quantitative Microvascular Biomarkers in Diabetic Retinopathy

Purpose: The purpose of this study was to evaluate the influence of optical coherence tomography angiography (OCTA) scan protocols on quantitative measurements of diabetic retinopathy (DR) biomarkers and their diagnostic performance for DR staging. Methods: In this cross-sectional study, 110 eyes from 74 treatment-naïve patients with DR underwent OCTA imaging using 6 × 6 mm, 12 × 12 mm, and 29 × 24 mm scan protocols. OCTA biomarkers, including nonperfusion index (NPI), intraretinal microvascular abnormalities (IRMAs) counts, and neovascularization (NV) counts, were analyzed. Receiver operating characteristic (ROC) analysis evaluated performance for discriminating proliferative DR (PDR) from nonproliferative DR (NPDR), and advanced-stage DR (severe NPDR and PDR) from early-stage DR (mild-moderate NPDR). Results: NPI and IRMA counts increased with wider scan protocols across DR severities, with higher NV detection in PDR on wider scans. NPI showed higher performance with 29 × 24 mm scans in discriminating PDR from NPDR (0.86; 95% confidence interval [CI] = 0.79-0.93) and advanced from early DR (0.92; 95% CI = 0.88-0.97) compared with smaller scan protocols. In 6 × 6 mm scans, the combined NPI and IRMA counts outperformed NPI for discriminating advanced from early DR (0.87; 95% CI = 0.81-0.94 vs. 0.81; 95% CI = 0.72-0.89) and PDR from NPDR (0.82; 95% CI = 0.74-0.91 vs. 0.73; 95% CI = 0.62-0.83). Conclusions: Wider scan protocols captured greater burden of nonperfusion and microvascular abnormalities. NPI serves as a robust standalone biomarker across protocols. When imaging is limited to smaller fields, combining NPI and IRMA counts improves staging performance. Translational Relevance: OCTA scan protocol selection influences quantitative assessment of DR biomarkers and may guide imaging strategies for clinical staging.