VARIATION IN THE MEASUREMENTS OF BASEMENT-MEMBRANE THICKNESS AND INFLAMMATORY CELL NUMBER IN BRONCHIAL BIOPSIES

We do not have an estimate of how much tissue is needed for a reliable measure of bronchial epithelial reticular basement membrane (RBM) thi ckness or for counts of inflammatory cells. An assessment of the frequ ency distribution and variance of data from repeat measurements of RBM thickness and biopsy section inflammatory cell counts in cases with a sthma (n=6), chronic obstructive pulmonary disease (COPD; n=5), and no rmal healthy subjects (n=7) was made. Tissue sections were stained wit h haematoxylin and eosin or by immunohistochemistry for EG2, mast cell tryptase and CD3-positive cells. Measurements of RBM thickness in ind ividuals followed a log-normal distribution. For a precision of approx imately +/-15%,31-45 measurements were required, In contrast, inflamma tory cell counts for each individual did not follow a normal distribut ion, There was high variance such that the cumulative weighted mean di d not become stable until at least 5-10 mm of tissue underlying the RB M had been included. In conclusion multiple measurements of reticular basement membrane thickness or tissue section cell counts should be ma de for each individual in studies of bronchial biopsies, It is recomme nded that reticular basement membrane thickness should be measured at 20 mm intervals over a 1 mm reticular basement membrane length and tha t a zone beneath it of at least 5-10 mm of reticular basement membrane should be included for counts of inflammatory cells.