[Do patients lie about smoking during follow-up in the respiratory medicine clinic?]

Quitting smoking is a first-line treatment for patients with bronchial diseases. Continued smoking worsens the clinical course of chronic broncho-pulmonary diseases and increases the number of exacerbations. Specialists commonly insist on the need to quit smoking. This study sought to determine whether a percentage of patients seen in a respiratory medicine clinic continued to smoke while denying doing so. One hundred twenty-five subjects were studied consecutively. At a regular visit they were first asked about smoking; later, without prior warning, exhaled carbon monoxide (CO) was measured by co-oximetry. If CO was over 10 ppm, the subject was considered to have been smoking. We defined a patient as a "liar" if he or she denied smoking but had a reading of CO in exhaled air over 10. Of the 125 cases studied, 21 (17%) smoked while denying doing so. Among men the percentage was 21%, and among ex-smokers, the figure was 27%. The highest value, 34%, was found among patients with chronic obstructive pulmonary disease (COPD). We conclude, therefore, that a substantial proportion of patients lies to their physicians. A third of COPD patients, who are particularly sensitive to the toxic effects of smoking, try to mislead their doctors.