Sputum sol-phase proteins and elastase activity in patients with cystic fibrosis

Sputum and serum samples were obtained from 38 patients with cystic fibrosis seen as out-patients at routine follow-up, or from patients admitted with acute pulmonary exacerbations of their disease. Elastolytic activity was measurable in the sputum of 13 of 16 out-patient samples and detectable in 21 of 22 patients admitted with pulmonary exacerbation. The enzyme activity was inhibited by soy bean trypsin inhibitor and alpha 1 antitrypsin, but not by ethylenediamine tetracetic acid, suggesting that it was predominantly a serine proteinase, probably leucocyte elastase. The mean sputum/serum albumin ratio was 2.53 X 10(-2) (SD +/- 2.4) for the out-patients and this was not significantly different from those of patients admitted with pulmonary exacerbation. However, those patients admitted with fever had increased sputum/serum albumin ratios (mean = 4.66 X 10(-2); SD +/- 3.19) compared with those admitted with a normal temperature (mean = 1.52 X 10(-2); SD +/- 0.41. 2p less than 0.01). The albumin ratios of the pyrexial group fell with antibiotic therapy. The sputum/serum alpha 1 antitrypsin ratios were generally greater than expected (by comparison with albumin) and evidence is presented suggesting that this is due to immunological over-estimation.