Development and comparison of two competitive ELISAs for estimation of cotinine in human exposed to environmental tobacco smoke

Abstract

We simultaneously set up two competitive (direct and indirect) enzyme-linked immunosorbent assays (ELISAs) based on the same antibody for estimation of cotinine (COT) in pregnant women especially and population generally exposed to environmental tobacco smoke. The results show that the limits of detection (LODs) for direct competitive ELISA and indirect competitive ELISA were 0.04 μgL-1 and 0.1 μgL-1, respectively. Direct competitive ELISA was found to be more sensitive than indirect competitive ELISA. Thereafter, we applied our direct competitive ELISA for the detection of COT from urinary samples taken from 450 volunteers from the Zhejiang Province of China. COT was detected in 100% of participants with concentration ranging from LOD to 5358.0 μgL-1. The GM and 95th percentile concentration of COT in pregnant women were 6.3 μgL-1 and 57.2 μgL-1, respectively. Males had statistically higher COT concentrations than females (P<0.0001), active smokers had statistically higher COT concentrations than non-smokers (P<0.0001), whereas, non-pregnant women were found to have higher COT concentration than pregnant women. We conclude that our developed direct competitive ELISA is useful for detecting the COT in urinary concentration of human. The human urinary data obtained in this study indicated that common people generally and pregnant women especially were highly exposed to COT. Further studies are needed to focus on the sources of exposure, potential health effects and risk assessment of exposure to COT.