Reduction of Eosinophilic Inflammation in the Airways: Sputum Induction and Eosinophil Counts

Sputum induction was performed as described previously. Medications were stopped for at least 12 h, after which sputum was induced by inhalation of increasing concentrations of hypertonic saline solution (0.9%, 1.8%, 3%, 4%, and 5%) until an adequate volume of sputum was collected. Patients were encouraged to cough deeply after each inhalation. Cell plugs in sputum were separated from saliva and collected. Sputum cells were then spread on the slides and treated with Wright-Giemsa so that the inflammatory cells could be counted. We reported the reproducibility of the proportion of sputum eosinophils by this method. The percentage of total eosinophils was determined by counting 900 inflammatory cells under a light microscope. All slides were independently counted by two readers blinded to treatment, study site, and visit. The average values of the percentage of sputum eosinophils were expressed. The sputum induction test was performed after the histamine challenge test.
Measurement of Airway Responsiveness to Histamine
Bronchial responsiveness to histamine was measured by a standard technique as described previously. Buy antibiotics online Patients inhaled doubling concentrations of histamine via nebulizer (model 646; DeVilbiss; Somerset, PA) for 2 min by tidal breathing. Increasing concentrations of histamine were administered until FEV1 decreased by > 20% of the baseline value. Results were expressed as the provocative concentration of histamine that caused a 20% decrease in FEV1 (PC20) from post-saline solution baseline. Bronchodilators were withheld for at least 12 h before the histamine challenge test, which was performed between 9 am and 10 am; all patients were tested on the same equipment and by the same investigator.
Peripheral Blood Measurement
Complete leukocyte counts, including differential cell counts, were evaluated on the days specified in the protocol.