Table 2

Comparison of smoking history between patients with rheumatoid arthritis and dermatology controls

	Current smokers (No (%))	Ex-smokers (No (%))	Never smoked (No (%))	Pack years (median (semi-IQR))^2-150
Patients (n=239)	100 (42)	55 (23)	84 (35)	18.0 (18.5)
Controls (n=239)	52 (22)	72 (30)	115 (48)	1.0 (8.5)
Significance (p value)	<0.001²	0.09^2-151	0.005^2-151	<0.001^2-152

↵2-150 Semi-IQR = semi-interquartile range.
↵2-151 Resulting from a sign test.
↵2-152 Resulting from a Wilcoxon signed rank test.