Table 2.

Comparing cases and controls on serum levels of cotinine, NNAL, PheT, and years of smoking

VARIABLES	Controls N=100	Cases N=100	Difference (controls-cases)	P
	Mean ± SDa	Mean ± SD	Mean ± SEb
Years of Cigarette Smoking	41.6 ± 7.2	45.4 ± 6.5	−3.9 ± 1.0	0.0001
Cotinine (ng/ml)	217 ± 111	227 ± 93	−10 ± 15	0.4681
Total NNALc (fmol/ml)	77.4 ± 39.3	92.4 ± 40.7	−15.0 ± 5.7	0.0084
PheTd (fmol/ml)	76.3 ± 66.8	92.5 ± 107.6	−16.1 ± 12.7	0.2039

^aSD = standard deviation

^bSE = standard error

^cNNAL = 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanol; total includes its glucuronides.

^dPheT = r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene