Controlling additionally for either FEV1 or FEV1/FVC ratio did not substantively alter the predictive relationship between MMP-9 and the outcomes and various measures of disease progression presented in Table 4, with the possible exception of COPD exacerbations; when controlling for FEV1, the number of COPD exacerbations predicted by a interquartile higher level of MMP-9 declined from 0.27 (95% CI 0.10 to 0.45; p = 0.003) to 0.17 (95% CI -0.02 to 0.36; p = 0.08) (Figure 3). This evidence concerns the gene MMP9 and chronic obstructive pulmonary disease.