Temporal stability of urinary and plasma biomarkers of tobacco smoke exposure among cigarette smokers

Intraindividual variability of measurements of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), nicotine, cotinine, and r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT) over time is uncertain. From 70 habitual smokers' plasma and urine sampled bimonthly for a year we analysed plasma for NNAL, cotinine and PheT, and urine for NNAL, cotinine and nicotine. We estimated the intraclass correlation coefficients (p(I)) for each measurement. Plasma and creatinine-corrected urinary NNAL were stable (p(I)>= 70%); plasma PheT and plasma and urinary total cotinine were fairly stable (p(I)>= 50%), but urinary nicotine p(I)approximate to 40% was not. Except for nicotine, single measurements from plasma or urine adequately represent individual mean exposure over time.