ANALYSIS OF PLASMA-PROTEIN LEAKAGE AND LEGAL SECRETION IN SPUTUM FROMPATIENTS WITH ASTHMA AND CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

In order to assess the usefulness of sputum analysis in studying plasm a-protein exudation and local secretion of proteins in the airways, we measured specific proteins in the sputum sol phase (SSP) and sputum g el phase (SGP) from patients with stable asthma or chronic obstructive pulmonary disease (COPD). Protein levels in SSP showed relatively sma ll variations between two subsequent visits of each patient (n = 22), as also reflected by intraclass correlation coefficients above 0.79. P rotein levels differed between SSP and SGP, but inclusion of the SGP d ata did not affect the variation of protein levels in sputum. The degr ee of plasma-protein leakage was estimated from the relative coefficie nts of excretion (RCE) of alpha(2)-macroglobulin and albumin (QA2M/QAL B), and of alpha(2)-macroglobulin and cerulop]asmin (QA2M/QCP), which do not depend on variable dilution of sputum. Despite the heterogeneit y of the study group of 26 patients with asthma (atopic [13] smokers [ 13], including five patients using inhaled steroids), QA2M/QALB and QA 2M/QCP correlated both with bronchial hyperreactivity (Spearman rank: r = - 0.45 and r = - 0.36, p < 0.05) and with blood eosinophil counts (r = 0.37 and 0.56, p < 0.05). We conclude that protein levels in SSP are relatively constant in patients with stable asthma or COPD; in pat ients with asthma, the plasma-protein leakage, as measured with the RC E in SSP, appears to correlate with indirect indices of airway inflamm ation.