Assessing tobacco use in an African population: Serum and urine cotinine cut-offs from South Africa



Publication Details

Ware, L. J., Charlton, K., Kruger, R., Breet, Y., van Rooyen, J., Huisman, H., Botha, S., Uys, A. S., Rennie, K. L., Naidoo, N., Kowal, P. & Schutte, A. E. (2019). Assessing tobacco use in an African population: Serum and urine cotinine cut-offs from South Africa. Drug and Alcohol Dependence, 195 82-89.


Background: Cotinine, a nicotine metabolite, is used to measure tobacco use and exposure, but recommended cut-offs to differentiate tobacco users from those exposed through the environment range from 3 to 58 ng/ml in serum, and 2.5 to 550 ng/ml in urine. Cut-offs may differ by ethnicity, sex and age. As data from adults in Africa are scarce, our aim was to evaluate cut-offs for serum and urine cotinine that best predict self-reported tobacco use in South African adults.

Methods: Two datasets were explored: African-PREDICT (n = 941 black and white healthy young adults, 20-30 years, serum cotinine); and WHO SAGE Wave 2 (n = 604 adults, 18-102 years, urine cotinine). Population specific cut-offs (ROC analyses) were compared with published cut-offs and self-reported tobacco use.

Results: Overall, 19% (293 of 1545) reported current tobacco use. The following cotinine cut-offs showed the highest sensitivity and specificity: serum ≥15 ng/ml in black and white men, and white women; serum ≥10 ng/ml in black women; urine ≥300 ng/ml for black, mixed ancestry, and older adults (50-plus years); urine ≥500 ng/ml for younger adults (18-49 years). Specificity was lower for urine than for serum cotinine.

Conclusion: Our study suggests that a serum cotinine level of ≥15 ng/ml and a urine cotinine level of ≥300 ng/ml best distinguish current tobacco users from non-users generally in the South African adult population.

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