Nicotine / Cotinine Testing
Tobacco smoking or passive inhalation of tobacco smoke results in the absorption of nicotine through the lungs and mucus membranes of the mouth. When nicotine is absorbed, it is readily metabolized into cotinine as its major metabolite. Cotinine is detectable in the urine of smokers even several days after the termination of smoking. Cotinine can only be derived from the metabolism of nicotine, and is therefore the best indicator of smoking status.
Willow labs performs a Cotinine Assay utilizing a homogeneous enzyme immunoassay. The assay is based on competition between cotinine labeled with glucose-6- phosphate dehydrogenase (G6PDH) enzyme and free cotinine in the sample for a fixed period of time. Nicotine and cotinine are rapidly eliminated by the kidney; the window of detection for cotinine in urine at a cutoff level of 200ng/mL is expected to be up to 2-3 days after cotinine use.