Methods to examine sputum for indices of airway inflammation are evolving. We have examined the repeatability and the validity of an improved method to measure sputum cells and fluid-phase eosinophil cationic protein (ECP), major basic protein (MBP), eosinophil-derived neurotoxin (EDN), albumin, fibrinogen, tryptase, and interleukin-5 (IL-5). Sputum was induced with hypertonic saline twice within 6 d in 10 healthy subjects, 19 stable asthmatics, and 10 smokers with nonobstructive bronchitis. The method included the processing of freshly expectorated sputum separated from saliva, treatment with a fixed proportion of dithiothreitol 0.1% followed by Dulbecco's phosphate-buffered saline, making cytospins, and collecting the supernatant. The reproducibility of measurements, calculated by the intraclass correlation coefficient, was high for all indices measured with the exception of total cell counts and proportion of lymphocytes. Asthmatics, in comparison with healthy subjects and smokers with bronchitis, had a higher proportion of sputum eosinophils (median percent 5.2 versus 0.5 and 0.3), metachromatic cells (0.3 versus 0.07 and 0.08), ECP (1,040 micrograms/L versus 288 and 352), MBP (1,176 micrograms/L versus 304 and 160), and EDN (1,512 micrograms/L versus 448 and 272). Asthmatics differed from healthy subjects, but not from smokers with bronchitis, in the proportion of neutrophils (46.9% versus 24.1%), albumin (704 versus 288 micrograms/mL), and fibrinogen (2,080 versus 440 ng/mL). Smokers with bronchitis showed a trend for a higher neutrophil count and levels of albumin and fibrinogen than healthy subjects. The proportion of sputum eosinophils correlated positively with ECP, MBP, EDN, albumin and fibrinogen levels, and metachromatic cell counts correlated with tryptase. In asthmatics, IL-5 correlated with eosinophil counts. There was a significant negative correlation between sputum indices and expiratory flows and methacholine PC20. Thus, the methods of measuring cell and fluid phase markers in induced sputum used in this study are reproducible and valid. They can therefore be used to reliably measure these indices of airway inflammation.

Background Airway inflammation is considered to be important in asthma but is relatively inaccessible to study. Less Airway inflammation is a major factor in the pathogenesis of asthma. Mast cell and eosinophil infiltration, epithelial damage, and mucus production are characteristic features.' Direct examination of the inflammatory response should help to improve understanding of the pathogenesis and treatment of asthma.In patients with stable asthma bronchial biopsy and bronchoalveolar lavage have been used to study airway inflammation2' but discomfort, inconvenience, and risks limit their use. Examination of sputum is a less invasive alternative,5 but sputum cannot always be produced spontaneously. When sputum is not otherwise available induced samples may allow secretions from the lower airways to be sampled.Sputum induction by inhalation of hypertonic saline has been successfully used to diagnose Pneumocystis carinii pulmonary infections in patients infected with HIV.'We adapted this method for use in asthmatic subjects and examined (a) the success rate and safety of the method, (b) the reproducibility of cell counts, and (c) the differences in cell counts between normal and asthmatic subjects. Methods SUBJECTSSeventeen normal subjects and 17 subjects with asthma were selected from among the staff (adults) and asthmatic patients and their siblings (adults or children) at the clinics of the Firestone Regional Chest and Allergy Unit and the Health Sciences Centre. All were nonsmokers or ex-smokers of more than five years. None had spontaneous sputum or symptoms of a respiratory tract infection, or had been exposed to a seasonal allergen within the last month. The normal subjects had no past or current symptoms of asthma, a forced expiratory volume in one second (FEVI) >80% of predicted values,9 a ratio of FEV, to vital capacity >70%, and normal airway responsiveness to methacholine (provocative concentration of methacholine causing a 20% fall in FEV, (PC20) >8 mg/ml)'0 (table 1). The asthmatic subjects had a history of episodic dyspnoea with wheeze in the previous six months and a PC20 methacholine <8 mg/ml (15 patients) or a spontaneous variability in peak expiratory flow rate (PEF of >20% (two patients). All were taking an inhaled 2 agonist when needed; 15 were treated with inhaled corticosteroid (daily dose 200-3000 Mg) and one with prednisone 5 mg daily. Although asthma was stable in all subjects, control of the condition was good" in only five subjects; the remaining 12 had more asthmatic symptoms

SummaryNon‐allergic bronchial hyper‐reactivity is a feature of most patients with asthma. We have measured non‐allergic bronchial reactivity to inhaled histamine and methacholine in thirteen asthmatic subjects before and after allergen inhalation in the laboratory. The allergen inhalation produced mild early asthmatic responses (19–40% FEV1 fall) in all thirteen, additional definite late asthmatic responses (17–29% FEV1 fall) in four, and equivocal late asthmatic responses (5–11% FEV1 fall) in five. Following allergen inhalation, non‐allergic bronchial reactivity increased in seven for up to 7 days. The seven included all four with definite late asthmatic responses and three of the five with equivocal late asthmatic responses. We conclude that allergens make asthma worse, partly through non‐allergic mechanisms, and that avoidance of allergens is important in reducing non‐allergic bronchial hyper‐reactivity.