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. 2017 May 18;313(3):L425–L452. doi: 10.1152/ajplung.00343.2016

Table 5.

Validated biological cut-point values separating smokers and nonsmokers

Biomarker Specimen Concentration
Carbon monoxide Breath 6 parts/million (169)
Cotinine Urine 31 ng/ml (96)
Cotinine Saliva/blood 3 ng/ml (21)
Cotinine Nasal lavage fluid 1 ng/ml (188)
NNAL Urine 47.3 pg/ml (96)
NNAL-to-cotinine ratio Urine 0.74 × 10−3 (96)
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