Estimating Cotinine Associations and a Saliva Cotinine Level to Identify Active Cigarette Smoking in Alaska Native Pregnant Women

Abstract

Studies indicate nicotine metabolism varies by race and can change during pregnancy. Given high rates of tobacco use and limited studies among Alaska Native (AN) women, we estimated associations of saliva cotinine levels with cigarette use and second-hand smoke (SHS) exposure and estimated a saliva cotinine cutoff to distinguish smoking from non-smoking pregnant AN women. Using questionnaire data and saliva cotinine, we utilized multivariable linear regression (n = 370) to estimate cotinine associations with tobacco use, SHS exposure, demographic, and pregnancy-related factors. Additionally, we estimated an optimal saliva cotinine cutoff for indication of active cigarette use in AN pregnant women using receiver operating characteristic (ROC) curve analysis (n = 377). Saliva cotinine significantly decreased with maternal age and significantly increased with cigarettes smoked per day, SHS exposure, and number of previous full term pregnancies. Using self-reported cigarette use in the past 7 days as indication of active smoking, the area under the ROC curve was 0.975 (95 % CI: 0.960–0.990). The point closest to 100 % specificity and sensitivity occurred with a cotinine concentration of 1.07 ng/mL, which corresponded to sensitivity of 94 % and specificity of 94 %. We recommend using a saliva cotinine cutoff of 1 ng/mL to distinguish active smoking in pregnant AN women. This cutoff is lower than used in other studies with pregnant women, most likely due to high prevalence of light or intermittent smoking in the AN population. Continued study of cotinine levels in diverse populations is needed.

Estimation of Saliva Cotinine Cut-Off Points for Active and Passive Smoking during Pregnancy—Polish Mother and Child Cohort (REPRO_PL)

“…In a large prospective study of Norwegian pregnant women the cut-off point for plasma cotinine concentration was 5.3 ng/mL, which is lower than that observed in our study [4]. Much lower cut-off values for saliva cotinine were noted for Alaska native pregnant women [11]. The differences between studies may result from many factors, including the ethnicity of the population, definition and prevalence of active (occasional and current smokers) and passive smoking, as well as methods used for cotinine assessment (including its LOD and LOQ).…”

“…We established a saliva cut-off value for active smoking status during pregnancy of 10 ng/mL, which is within the range previously reported in other studies (1–24 ng/mL) [2,9,11,14,15]. Based on a comprehensive review of biomarker verification of tobacco use and cessation, similar to our results, 10 ng/mL was recommended for the cut-off concentration to distinguish pregnant smokers from non-smokers [2].…”

“…As the example, in the study by Benowitz et al the following optimal serum cotinine concentrations for discriminating smokers from non-smokers were proposed: 5.92 ng/mL, 4.85 ng/mL, and 0.84 ng/mL for non-Hispanic blacks, non-Hispanic whites, and Mexican Americans, respectively [5]. In addition, some policy and interventional activities that came into play in recent years might have led to a decrease in cut-off point over time as a result of reductions in smoking intensity or ETS exposure [11]. …”

“…In order to identify pregnancies at risk, public health practitioners need to have an objective measure of tobacco exposure [11]. Based on our data, verification of self-reported smoking status by biochemical measurements might be needed in the case of less educated women and for appropriate ETS assessment.…”

“…Previous studies have recommended saliva cotinine cut-off concentrations ranging from 1 ng/mL to 24 ng/mL to indicate active smoking among pregnant women [2,9,11,12,13,14,15]. It is important to be aware of interindividual variability in metabolism of nicotine and cotinine [16], which may be partly under genetic control [17].…”