Figure 2.

Relationship between Subtype and Stage Inference (SuStaIn) stage and lung function. (A) Scatterplot of cross-sectional spirometry versus SuStaIn stage for the Tissue→Airway and Airway→Tissue subtypes. A linear and a quadratic model are fitted to the data via a least-squares estimation to gauge the relationship between SuStaIn stage and markers of lung function. In the Tissue→Airway subtype, there is a visible nonlinear relationship between lung function and SuStaIn stage, with a more rapid decrease in lung function at earlier SuStaIn stages. The decline in lung function in the Airway→Tissue subgroup is linear and less rapid at earlier SuStaIn stages. (B) Scatterplot of measured decline in spirometry versus baseline SuStaIn stage for the Tissue→Airway and Airway→Tissue subtypes in Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1–2 subjects. In both the Tissue→Airway and Airway→Tissue subtypes, SuStaIn stage at baseline correlated with future decline in lung function measured using FEV₁/FVC.