Total eosinophil cationic protein levels in induced sputum as a marker of changes in eosinophilic inflammation in a patient with allergic asthma.

BACKGROUND

Counting eosinophils in induced sputum seems to be a better way to survey disease activity than indirect clinical assessments of airway inflammation, such as pulmonary function measurement. The conventional analysis of induced sputum, however, is time-consuming and requires skilled personnel, which have restricted its use.

OBJECTIVE

To determine whether measuring eosinophil cationic protein (ECP) levels in the entire sputum sample could replace the method of counting eosinophils and measuring ECP levels in the supernatant only to establish a clinically more applicable method of studying the intraindividual changes in eosinophilic activity in induced sputum.

METHODS

In 13 patients with mild, nonsymptomatic allergic asthma, sputum was induced before and 24 hours after allergen challenge. The entire sputum sample was diluted with 0.1% dithiothreitol, incubated, and divided into 2 parts. One part was processed according to the conventional method, and released ECP levels in the supernatant were measured. The second part was treated with a lysing reagent. Cell debris was separated, and total (intracellular and extracellular) ECP levels in the solution were measured.

RESULTS

We found good correlation between total ECP levels in the entire sputum sample and released ECP levels in the supernatant before (r = 0.97) and 24 hours after (r = 0.99) allergen challenge (P < .01 for both). We also found a good correlation between the changes in total and released ECP levels (r = 0.99; P < .01).

CONCLUSIONS

Total ECP concentration seems to reflect the eosinophilic inflammatory changes in asthma and might be a useful tool in clinical practice.