Fig. 4
From: Relationships of serum CC16 levels with smoking status and lung function in COPD
Relationship between FEV1/FVC and CC16 level is modified by smoking status among those with COPD (N = 245). The linear regression interaction plot depicts the statistically significant interaction effects between log CC16 level and smoking status on FEV1/FVC in COPD (Pinteraction = 0.01). Presented are regression lines and 95% confidence intervals of the model estimated slopes for each smoking status calculated at fixed values of other variables in the model. For former smokers with COPD, FEV1/FVC increased with each unit increase in log CC16 level, while an inverse relationship was noted for never and current smokers with COPD. Along with the dependent variable, the model included the interaction term (CC16 * smoking status), the main effects of smoking status and log CC16 level, age, BMI, pack-years, assay plate number, and inhaled and systemic steroid use