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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.
