Induced sputum cell counts in healthy adults

Induced sputum cell counts provide a relatively noninvasive method to evalu ate the presence, type, and degree of inflammation in the airways of the lu ngs. Their interpretation requires a knowledge of normal values from a heal thy population. The objective was to examine the total and differential cel l counts in induced sputum from a sample of healthy adults. A total of 118 healthy nonsmoking adults were studied. None had asthma or airflow obstruct ion (negative history, FEV1 greater than or equal to 80% predicted, ratio o f FEV1 to vital capacity [FEV1/VC] greater than or equal to 80%, methacholi ne PC20 greater than or equal to 16 mg/ml). Forty-six were atopic. Sputum i nduction produced an adequate sample in 96 subjects [53 males, mean age (ra nge) 36 (18 to 60) yr]. The expectorate was processed within 2 h; sputum wa s selected, treated with dithiothreitol, filtered, and examined in a hemocy tometer for total cell count and viability and on Wright-stained cytospins for a differential cell count. The mean, median (90th percentile) total cel l count was 4.1, 2.4 (9.7) x 10(6) cells/g and cell viability was 69.6, 72. 0 (89.7)%. The proportions of eosinophils were 0.4, 0.0 (1.1)%, neutrophils 37.5, 36.7 (64.0)%, macrophages 58.8, 60.8 (86.1)%, lymphocytes 1.0, 0.5 ( 2.6)%, metachromatic cells 0.0, 0.0 (0.04)%, and bronchial epithelial cells 1.6, 0.3 (4.4)%, respectively. Female gender and atopy were associated wit h a significant elevation of eosinophils; mean difference between male/fema le was 0.3% (p = 0.043) and between atopic/nonatopic 0.4% (p = 0.024). This study has identified reference values for total and differential cell coun ts in induced sputum of healthy adults.