Passive Smoking and Lung Disease Workup

Updated: Oct 07, 2021
  • Author: Timothy D Murphy, MD; Chief Editor: Girish D Sharma, MD, FCCP, FAAP  more...
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Laboratory Studies

The diagnosis of passive smoking exposure (secondhand smoke) is primarily obtained by history.

Urinary cotinine levels have limitations and widely vary between individuals. As many as 50% of nonsmokers may show urinary cotinine, demonstrating the ubiquity of the exposure. Levels are generally low and are less than 1% of those found in smokers.

Cotinine is a biomarker of environmental tobacco smoke (ETS) exposure but may not be related to the adverse effect under study. Cotinine may not be specific for ETS exposure because dietary nicotine (eg, eggplant, green pepper, tea, tomato) may elevate cotinine levels. Salivary or serum levels may also be measured. Measuring hair cotinine levels in children exposed to ETS may prove a more sensitive biomarker of exposure.

Outside of a clinical history, questionnaires are the most common method to attempt to quantitate ETS exposure, but these can be limited by a lack of understanding of the questionnaire, bias, faulty memory, or intentional alteration of answers.


Histologic Findings

Kim et al investigated the relationship between exposure to secondhand smoke and lung cancer by histologic type on the basis of pooled data from 18 case-control studies in the International Lung Cancer Consortium. [15] Their data included those for 2,504 never-smoker case patients and 7,276 never-smoker control individuals; and 10,184 ever-smoker case patients and 7,176 ever-smoker control individuals. The researchers used multivariable logistic regression, adjusted for age, sex, race/ethnicity, smoking status, and pack-years of smoking. Among never-smokers, the odds ratios (ORs) comparing those ever exposed to secondhand smoke with those never exposed were 1.31 for all histologic types combined, 1.26 for adenocarcinoma, 1.41 for squamous cell carcinoma, 1.48 for large-cell lung cancer, and 3.09 for small-cell lung cancer. The estimated association with secondhand smoke exposure was greater for small-cell lung cancer than for non–small-cell lung cancers (OR, 2.11). The investigators concluded that the association with secondhand smoke is stronger for small-cell lung cancer than for cancers of other histologic types. [15]