Optimal Carbon Monoxide Criteria to Confirm Smoking Status Among Postpartum Women

Introduction: Although expired-air carbon monoxide (CO) is a well characterized biomarker of cigarette smoking, limited research has assessed whether the standard clinical CO cutoffs need to be altered for postpartum women and whether these cutoffs remain constant across the postpartum year. Accordingly, the present study evaluated the effectiveness of using CO as a method to confirm smoking status relative to salivary cotinine among postpartum women and assessed optimal CO criteria to confirm smoking status across the postpartum year. Differences in optimal CO criteria to confirm smoking status also were examined between black and white postpartum women. Methods: Women (N = 208) for the present study had quit smoking for their current pregnancy and were enrolled in a larger postpartum relapse prevention intervention. Smoking status was assessed at 12, 24, and 52 weeks postpartum using both expired-air CO and salivary cotinine. Results: Receiver-operating characteristic analyses indicated that CO provided moderately high diagnostic accuracy to distinguish between women who were and were not smoking when using salivary cotinine as the reference criterion to confirm smoking status. CO cutoffs of 2 and 3 parts per million (ppm) had the highest overall efficiency and combined sensitivity and specificity across the postpartum year. Results were consistent for black and white women. Conclusions: These findings indicate that optimal CO criteria to confirm smoking status remains stable throughout the postpartum year and support a need to utilize CO cutoffs much lower than the standard clinical CO criterion of 8 ppm to confirm abstinence among postpartum women. Implications: Findings from the present study confirm the value of CO as a biomarker of smoking status among postpartum women. Results indicate that CO cutoffs of 2 and 3 ppm were optimal for confirming smoking status across the entire postpartum year in both black and white women. These findings offer a replication and extension of previous work and indicate that optimal CO criteria to confirm smoking status remain stable throughout the postpartum period and further support a need to utilize CO cutoffs much lower than the standard clinical criterion of 8 ppm to confirm smoking status among postpartum women.