Oscillometry-defined small airway dysfunction as a predictor of moderate-to-severe exacerbations in COPD: a systematic review and meta-analysis

Small airway dysfunction (SAD) is a pivotal feature of chronic obstructive pulmonary disease (COPD), yet spirometry has limited sensitivity for peripheral airway impairment. Oscillometry offers effort-independent assessment of respiratory mechanics during tidal breathing. We systematically reviewed longitudinal studies reporting the association between baseline oscillometry and subsequent moderate-to-severe acute exacerbations (AE) in COPD, and compared its predictive accuracy with spirometric indices. Effect estimates (OR, HR, IRR) were pooled using a random-effects model (DerSimonian–Laird). Eight studies (4,175 independent patients; follow-up 1–6 years) met inclusion criteria, five contributing to the meta-analysis. Patients with oscillometry-defined SAD had a 2.18-fold higher risk of moderate-to-severe AE (95% CI 1.49–3.20; I² = 49.8%; P < 0.001). In four studies reporting both indices, oscillometry and FEV₁ showed comparable discrimination for AE (AUC 0.775 vs 0.777), whereas a combined model achieved superior discrimination (AUC 0.860). Patients with GOLD stage 1 COPD and abnormal oscillometry had exacerbation risk comparable to GOLD stage 2, indicating that oscillometry identifies at-risk patients missed by spirometry alone. Oscillometry-defined SAD independently predicts COPD exacerbations and provides incremental prognostic value over spirometry, supporting its integration into a precision-medicine approach. Further studies should validate oscillometric cut-offs for risk stratification.