Reference value of induced sputum cell counts and its relationship with age in healthy adults in Guangzhou, Southern China

Abstract Purpose To establish the reference value of total and differential cell counts in induced sputum in healthy adults in Guangzhou, and to explore the relationship of age and gender with sputum cell counts. Methods A total of 185 healthy, nonatopic, never‐smokers between 19 and 74 years old underwent induced sputum test with hypertonic saline (3%) inhalation. Sputum samples were collected for total and differential cell counts. Results Qualified sputum samples were obtained from 153 subjects (mean age: 43 ± 17) with a success rate of 82.7% (153/185). The mean Standard Deviation (STDEV) and 2.5% to 97.5% percentile total cell counts were 2.1 × 106/g (1.0), (.7–4.5 × 106/g). The mean STDEV and 2.5% to 97.5% percentile differential cell counts were as follows: neutrophil 38.3% (17.7), (8.9%–72.9%); macrophage 58.9% (17.7), (24.7%–90.0%); eosinophils: median, .3%; interquartile range (IQR), 1.1%; and .0% to 95.0% percentile, .0% to 2.0%; and lymphocytes: median, 1.0%; IQR, 1.8%; and .0% to 95.0% percentile, .0% to 4.5%. There was positive correlation of age with the percentage of neutrophil and eosinophil (r = .659, r = .402; P < .001). The percentage of neutrophil, macrophage and eosinophil were significantly different among different age groups. The total cell counts and sputum cell counts were comparable between males and females. Conclusions This study initially establishes reference value of induced sputum cell counts in healthy adults in Guangzhou, Southern China, and it verifies that neutrophilic and eosinophilic counts increase by age.