Clinical Usefulness of Induced Sputum Cell Differentials as Monitoring Indices of Asthmatic Airway Inflammation

Jang, An Soo; Choi, In Seon; Lee, Shin Seok; Park, Seog Chea; Kang, Kwang Won; Lim, Ho; Kim, Young Chul; Park, Hyung Jun; Park, Kyung Ok

Abstract

BACKGROUND
Asthma is characterized by reversible airway obstruction and chronic airway inflamation. Inflammatory cells such as eosinophils, T-lymphocytes, mast cells, neurtrophils, epithelial cells play an important role. Airway inflammation in asthma can be evaluated directly by bronchoscopy, bronchoalveolar lavage, and indirectly by peripheral blood. Analysis of sputum induced by hypertonic saline inhalation, a noninvasive method, may provide a useful investigational and clinical tool in asthma. SUBJECTS: Forty eight asthmatics and 18 control subjects were studied. Inclusion criteria for asthmatic subjects were a history of symptoms of asthma, bronchial hyperreactivity to methacholine (PC20FEV1< or =16mg/ml) and airway reversibility after antiinflammatory drug medication. Asthma was classified by the guideline of 1992 International Consensus Report on diagnosis and treatment asthma.
METHODS
After premedication with inhaled salbutamol 200microg, Subjects inhaled hypertonic saline solution (3%) aerosol for 20-30min until adequate volume of sputum expectorated. FEV1 measured before, during and after induction of sputum. Sputum was collected in a sterile plastic container and treated by adding equal volumes of 0.1% dithiothreitol followed by equal volumes of Dulbecco's phosphate buffered saline (D-PBS). The sample was well mixed and filtered through a gauze. The filtrate was centrifuged and the cell pellet was resuspended in D-PBS and then total cell count of nonsquamous cells was measured. Crtospin preparations were obtained. Differentials of 400 nonsqamous cells were measured by two observers.
RESULTS
1. The proportion of eosinophils in induced sputum was significantly higher in patients with asthma compared with control subjects (19.1+/-3.4% vs 1.7+/-0.3%, p<0.01), but macrophage in asthmatics was significantly lower than that of control subjects (60.1+/-4.3% vs 85.3+/-1.9%, p<0.01). 2. Moderate or severe ashmatics compared to mild asthmatics, had significantly higher proportion of eosinophils (33.7+/-6.7%, 29.3%+/-8.7% vs 5.2+/-1.5%, p<0.05, respectively). 3. The proportion of eosinophils decreased significantly after antiasthma therapy from 43.8+/-0.47% to 4.0+/-0.76% (p<0.01). 4. FEV1 was significantly negatively correlated with the proportion of eosinophils, but serum eosinophil count was positively correlated with the proportion of eosinophils in induced sputum (r=-0.732, p<0.01). 5. Mean time of sputum induction was 14.2 min in asthmatics and 20.1 min in control subjects. Mean volume of sputum was 2.1 ml in asthamtics and 1.9ml in control subjects. None of the subjects experienced bothersome symptoms during inhalation of hypertonic saline except three patietns. CONCULSION: We concluded induced sputum examination is a feasible and noninvasive method of investigation of airway inflamation and a good tool evaluating the effect of treatment and follow up bronchial asthma.