an increasing trendP < 0.0001
MMP-8 levels also showed an increasing trend ( P < 0.0001) with increasing pack-year category, although no trend was seen with MMP-9 levels (Additional file 4 ).
MMP-8 levels also showed an increasing trend ( P < 0.0001) with increasing pack-year category, although no trend was seen with MMP-9 levels (Additional file 4 ).
There was also a significant trend ( P = 0.0005) of increasing PC3 level with increasing pack-year category (Table 6 ).
No association was found with CRP levels, although this approached significance ( P = 0.07) in models that did not include MMP-8.