Particle counting immunoassay for urinary cotinine. Comparison with chromatography, enzyme-linked immunoassay and fluorescence polarization immunoassay

Cotinine excretion (tobacco smoke biomarker) of smokers and non-smokers: comparison of GC/MS and RIA results

With a validated GC/MS method, the tobacco smoke biomarker cotinine has been estimated in urine for 148 non-smokers (male; 43 +/- 13 years; median 5.0 micrograms/g creatinine; 95th percentile 104 micrograms/g) and 96 smokers (male; 39 +/- 12 years; 1002 micrograms/g; 2993 micrograms/g). For a subgroup of 50 persons, the GC/MS results were compared with those by a commercially available radio immunoassay. Both methods identified the same persons as non-smokers and smokers, respectively, and were closely related. For smokers, the relationship was distinctly closer than for the non-smokers (r = 0.90, p < 0.001, n = 14 vs. r = 0.41, p < 0.02, n = 36). The RIA values were 2.4 times (smokers) and 2.9 times (non-smokers) higher than the GC/MS results. This was probably caused by the cross reactivity of the RIA antibodies against other urinary nicotine metabolites, e.g. trans-3'-hydroxycotinine, and has to be taken into account to correctly compare results of studies obtained with different analytical techniques and for choosing cut-off points to discriminate between active smokers and non-smokers of between non-smokers with higher or lower exposure to environmental tobacco smoke.

Is the hair nicotine level a more accurate biomarker of environmental tobacco smoke exposure than urine cotinine?

STUDY OBJECTIVE

The aim of this study was to compare the two biomarkers of exposure to environmental tobacco smoke (ETS); urine cotinine and hair nicotine, using questionnaires as the standard.

DESIGN

A cross sectional study of children consecutively admitted to hospital for lower respiratory illnesses during the period of the study.

SETTINGS

Three regional hospitals in the larger Wellington area, New Zealand.

PARTICIPANTS

Children aged 3-27 months and admitted to the above hospitals during August 1997 to October 1998. A total of 322 children provided 297 hair samples and 158 urine samples.

MAIN RESULTS

Hair nicotine levels were better able to discriminate the groups of children according to their household's smoking habits at home (no smokers, smoke only outside the home, smoke inside the house) than urine cotinine (Kruskall-Wallis; chi(2)=142.14, and chi(2)=49.5, respectively (p<0.0001)). Furthermore, hair nicotine levels were more strongly correlated with number of smokers in the house, and the number of cigarettes smoked by parents and other members of the child's households. Hair nicotine was better related to the questionnaire variables of smoking in a multivariate regression model (r(2)=0.55) than urine cotinine (r(2)=0.31).

CONCLUSIONS

In this group of young children, hair nicotine was a more precise biomarker of exposure to ETS than urine cotinine levels, using questionnaire reports as the reference. Both biomarkers indicate that smoking outside the house limits ETS exposure of children but does not eliminate it.