Table 4. Blood biomarkers, smokers versus never smokers, intent-to-treat sample, week 0.

		Smokers			Never smokers
Marker	Units	n	Mean	SD	n	Mean	SD
Cotinine	nmol/L	108	1.60	0.62	27	0.004	0.002
COHb	% saturation	130	6.10	1.94	32	1.21	0.38
4-ABP-Hb	pg/g Hb	116	63.6	29.2	31	11.9	15.1

p < 0.05 for all. See Table 2 for abbreviations.