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Biomarkers of Smoking - Which Cut-Off Values Should be Used? Abstract. Verification of smoking status by means of biomarkers is important for treatment decisions of patients with smoking-related diseases. Cotinine is currently the best biomarker to document nicotine consumption. A low cost alternative method to determine smoking status is by measurement of carboxyhemoglobin (CO-Hb) in the exhaled breath. The main disadvantage of CO-Hb is the short half-life. The appropriate cut-off value for active nicotine consumption in Switzerland is 50 ng/ml or higher cotinine in the urine or 10 ng/ml and 12 ng/ml in serum and saliva, respectively. CO-Hb levels greater than 2 % indicate smoking with high probability, levels above 3 % with very high probability.

An epidemiological study into the influence of cotinine validated maternal smoking and antioxidant vitamin concentrations on new born infants was carried out from 1992 to 1994 in the Department of Obstetrics and Gynaecology, University of Homburg/Saar. Of 222 participated pregnant women 26% were active smokers and 46% passive smokers. After adjustment a mean reduction in birth weight of 228 g was found in infants born to smokers, without dose correlation. Birth weight was not significantly reduced in infants born to passive smokers. There was no influence to the gestational age. A high correlation was established between maternal serum cotinine and umbilical cotinine (r = 0.91). In actively smoking mothers there was a positive correlation between vitamin E concentration and corrected infant birth weight (r = 0.33). Actively smoking mothers with children with a birthweight lower than the 25th percentile had significantly (p < 0.007) oftener lower vitamin E concentrations. Smoking increases the consumption of vitamin E, so that there is overproduction of peroxides and a reduction in prostacyclin. This lack of prostacyclin may lead to diminished perfusion of the placenta and may explain the birth weight reduction in smoker children.

The effects after smoking cigarettes with different nicotine content (1.5 mg and 0.08 mg nicotine/cigarette) were investigated in 6 healthy habitual smokers. Carboxyhemoglobin (COHb) and plasma nicotine levels were determined at the same time as circulatory parameters, heart rate and blood pressure together with metabolic parameters like blood sugar, lactate, free fatty acids and plasma dopamine-beta-hydroxylase (DBH) and plasma cortisol. With the exception of COHb the parameters investigated were shown to be dependent on the nicotine levels. For blood pressure, heart rate and lactate the peaks appeared simultaneously with the maximum nicotine levels, whereas for DBH, cortisol, blood sugar and the free fatty acids there was a delayed reaction in comparison with the nicotine levels. The parameters investigated are not affected by COHb with levels up to 5.6 +/- 0.5%. These results show that after cigarette smoking, nicotine causes considerable changes in the circulation and metabolism.

It is unclear whether passive smoking has any deleterious effects on pregnancy. The few investigations performed up to date seem to imply that passively inhaled cigarette smoke has teratogenic potential. To examine the extent of passive smoking during pregnancy detailed smoking histories were obtained from 442 pregnant women. Whereas only one in five women smoked actively during pregnancy, one in three women had a history of passive smoking. In additional 101 pregnant women serum-cotinine levels were determined. With this additional parameter it was possible to make a much more detailed determination of actual exposure to tobacco smoke than by using history alone.