Table 6

Association between principal component 3 and pack-year category

Variable

0 pack years (n = 61

1 to 15 pack years (n = 37)

16 to 30 pack years (n = 17)

> 30 pack years (n = 14)

P (trend)a


PC3

-0.10 (1.80)

0.38 (1.17)

0.79 (1.21)

1.86 (2.51)

< 0.0005


Mean (standard deviation) values are shown. PC, principal component. aLinear test for trend.

Mattey et al. Arthritis Research & Therapy 2012 14:R127   doi:10.1186/ar3857

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