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Updated: May 30, 2026

Measuring Carbon Content in Airway Macrophages Exposed to Carbon-Containing Particulate Matters
Published on: July 12, 2024
Lipid and smoker's inclusions in sputum macrophages in patients with airway diseases
Andrew M Wilson1, Parameswaran Nair, Frederick E Hargreave
1Firestone Institute for Respiratory Health, St Joseph's Healthcare and Department of Medicine, McMaster University, 50 Charlton Avenue East, Hamilton, Ontario, Canada L8N 4A6.
Abstract:
We studied the effect of tobacco smoking on macrophage lipid index and macrophage smokers inclusions in induced sputum in 256 patients (143 non-smokers, 81 ex-smokers and 32 current smokers). Lipid index was, using the Oil red O stain, the sum of the lipid staining droplet score (range 0-4) in 100 macrophages. Smokers inclusions were assessed using Wright's stain and graded as "none", "few", "moderate" or "many". Lipid index was significantly higher in current smokers (112.5, SD 58.5 units) than ex-smokers (29.2, SD 42.8 units) or non-smokers (13.4, SD 121.7). Smokers inclusions were present in all current smokers but only in 2 non-smokers. The mean smoking history of current smokers with few macrophage inclusions was 15.0 (SD 11.2), moderate 21.6 (SD 15.7), and many 30.0 (SD 21.9) pack years. There was a significant difference between the length of time ex-smokers had quit smoking if they had no or few smokers inclusions (mean 17.6 (SD 11.2) years) compared to those with moderate or many smokers inclusions (mean 2.8 (SD 5.8) years) (p = 0.01). Lipid index was significantly correlated with smokers inclusions (r = 0.72, p < 0.01). We conclude that smoker's inclusions within sputum macrophages is a reliable indicator of cigarette smoking and that the sputum lipid index cannot be used as an assessment of oropharyngeal reflux in cigarette smokers.
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