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bronchial biopsies mainly sample the proximal con- ducting airways and it has perhaps been surprising to find the extent of inflammation and remodelling which occurs rs throughout the relatively large airways in asthma. biop- sies sample only a fragment of the surface of a very large bronchial tree and it has been reassuring to note that the largest contribution to variation is between subjects rather than between distinct generations of airway. variation between biopsies taken from a single airway is relatively low but variation between step sections of a sin- gle biopsy is high and it is important to sample several random step sections of each biopsy to represent adequat- ely the inflammatory cell of interest . it is important to quantify separately distinct zones of the bronchial muc- osa. the inflammatory cell which predominates within the surface epithelium may be quite different to that in the tis- sue immediately beneath, or that which surrounds or is within the bronchial glands. for example, bronchoalveo- lar lavage (bal) fluid obtained from subjects with smok- ers bronchitis is rich in neutrophils yet it is our experience that the subepithelial tissues of bronchial bi- opsies obtained from these subjects show a scarcity of this cell type. however, examination following application of an antibody directed against neutrophil elastase shows an abundance of positive cross reactivity within the surface epithelium which is not found beneath it. this may, in part, explain the difference between the results of bal and biopsy. the correlations between cellular findings at bal, and biopsy are known to be poor, the correlations between bronchial brush biopsies and counts of surface epithelium obtained by biopsy are not known and these associations should be examined in the future. there is an association between eosinophil count in sputum and biop- sy suggesting this may be a less invasive way to assess eosinophil infiltration in the airway wall but the results for other cell types have been disappointing. it is the author's opinion that bronchial biopsy still remains the gold standard for assessing inflammatory events ongoing in the airway mucosa, and that other assessment techni- ques may provide complementary but information quite distinct from that obtained in biopsies.

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