Isotope Dilution HPLC–MS/MS Analysis of Serum Cotinine Reveals Environmental Tobacco Smoke–Associated PID Risk

Pelvic inflammatory disease (PID), a common gynecologic condition linked to infertility, ectopic pregnancy, and reproductive tract cancers, has long been associated with smoking; however, the impact of environmental tobacco smoke (ETS) on non-smoking women remains unclear. Previous studies have depended on self-reported exposure, which may be inaccurate. In response, a joint study between the Affiliated Hospital of Jiangnan University (Wuxi, People's Republic of China) and Donghai People's Hospital (People's Republic of China) investigated the association between serum cotinine (a stable nicotine metabolite that serves as an objective biomarker of tobacco exposure) levels and PID risk in non-smoking women using data from the National Health and Nutrition Examination Survey (NHANES). ETS exposure was assessed using serum cotinine measured by isotope dilution high-performance liquid chromatography with tandem mass spectrometry (HPLC–MS/MS). A paper based on this work was published in the Journal of Obstetrics and Gynaecology (1).

An inflammatory disorder of the female upper genital tract, PID results from an infection that can involve the uterus, fallopian tubes, ovaries, and pelvic peritoneum (2).Accounting for 94% of sexually transmitted infection (STI)-related morbidity in women in high-income countries, the burden of PID is particularly pronounced in the United States; its prevalence is approximately 4.4%, a rate substantially higher than the global age-standardized prevalence (∼0.053%) (3–5).

While PID is rarely directly life-threatening, it carries significant long-term consequences. Results from the Pelvic Inflammatory Disease Evaluation and Clinical Health (PEACH) research revealed that around 32% of participants experienced chronic pelvic discomfort, 18% encountered infertility, and between 0.6% and 2.0% confronted ectopic pregnancies (6). In addition, the chronic inflammatory state associated with PID may lead to serious outcomes. As a recurrent infection, PID causes chronic inflammation, tissue damage, and scarring—conditions that may promote carcinogenesis through repeated epithelial injury, increased cytokine and growth factor production, oxidative stress, and DNA damage (7).

This cross-sectional study included 3718 non-smoking women aged ≥18 years from NHANES 2013–2020. As stated previously, ETS exposure was assessed using serum cotinine measured by isotope HPLC–MS/MS, with cotinine levels categorized as unexposed, low, or high exposure. PID was identified based on self-reported treatment for pelvic infections. Weighted logistic regression was used to examine associations between cotinine and PID, adjusting for confounders identified by a directed acyclic graph. In addition, restricted cubic spline and subgroup analyses were conducted (1).

The research indicated that, among participants, 3.1% reported a history of PID. Those with PID had higher serum cotinine levels. In fully adjusted models, each one-unit increase in log₂-transformed cotinine was associated with a 10% increase in PID risk (OR = 1.10; 95% CI: 1.02-1.19). High ETS exposure (≥3 ng/mL) was linked to a significantly higher risk of PID compared to unexposed individuals (OR = 2.53; 95% CI: 1.05–6.08). A linear dose-response relationship was observed. Subgroup analyses showed consistent results across all strata (1).

According to the authors (1), the study “provides novel epidemiological evidence that objectively quantified exposure to environmental tobacco smoke, via serum cotinine, is significantly associated with an increased risk of pelvic inflammatory disease in non-smoking women. This finding underscores that second-hand smoke is a modifiable risk factor for PID, extending prevention strategies beyond active smoking.” The authors recommend that future research prioritize prospective cohorts to confirm causality and mechanistic studies “to elucidate how ETS-induced inflammation compromises reproductive tract defenses” (1).

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References

1. Ye, M.; Wu, H.; Shan, F. et al. Environmental Tobacco Smoke Exposure and Pelvic Inflammatory Disease: A Cross-Sectional Analysis of Serum Cotinine. J. Obstet. Gynaecol. 2026, 46 (1), 2617560. DOI: 10.1080/01443615.2026.2617560
2. Benowitz, N. L.; Bernert, J. T.; Caraballo, R. S. et al. Optimal Serum Cotinine Levels for Distinguishing Cigarette Smokers and Nonsmokers Within Different Racial/Ethnic Groups in the United States Between 1999 and 2004. Am. J. Epidemiol. 2009, 169 (2), 236–248. DOI: 10.1093/aje/kwn301
3. Hillier, S. L.; Bernstein, K. T.; Aral, S. A Review of the Challenges and Complexities in the Diagnosis, Etiology, Epidemiology, and Pathogenesis of Pelvic Inflammatory Disease. J. Infect. Dis. 2021, 224 (12 Suppl 2), S23–S28. DOI: 10.1093/infdis/jiab116
4. Kreisel, K. M.; Llata, E.; Haderxhanaj, L. et al. The Burden of and Trends in Pelvic Inflammatory Disease in the United States, 2006-2016. J. Infect. Dis. 2021, 224 (12 Suppl 2), S103–S112. DOI: 10.1093/infdis/jiaa771
5. He, D.; Wang, T.; Ren, W. Global Burden of Pelvic Inflammatory Disease and Ectopic Pregnancy from 1990 to 2019. BMC Public Health 2023, 23 (1), 1894. DOI: 10.1186/s12889-023-16663-y
6. Hunt, S.; Vollenhoven, B. Pelvic Inflammatory Disease and Infertility. Aust. J. Gen. Pract. 2023, 52 (4), 215–218. DOI: 10.31128/AJGP-09-22-6576
7. Piao, J.; Lee, E. J.; Lee, M. Association Between Pelvic Inflammatory Disease and Risk of Ovarian Cancer: An Updated Meta-Analysis. Gynecol. Oncol. 2020, 157 (2), 542–548. DOI: 10.1016/j.ygyno.2020.02.002