Table 8

Relationship between pack-year category and frequency of AS patients in low and high MMP clusters

Pack years

Low MMP cluster

High MMP cluster

0

46 (73.0)

17 (27.0)

1 to 15

19 (52.8)

17 (47.2)

16 to 30

8 (47.1)

9 (52.9)

> 30

5 (35.7)

9 (64.3)^a

Data presented as n (%). AS, ankylosing spondylitis; MMP, matrix metalloproteinase. ^aP (trend) = 0.001 (Cochrane-Armitage test for trend).

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