Background: Eosinophil granulocytes play an important role in allergic inflammation of the nasal mucosa. Eosinophil cationic protein (ECP) is a specific eosinophil granule protein released upon activation of these cells. ECP concentration in nasal secretions has been demonstrated to be a good marker for the activity of eosinophilic nasal mucosal inflammation. The clinical use of such a marker requires defined values which are regarded as pathological or within normal range. In analyses of nasal secretion samples, the sampling method has an important influence on the data obtained.
Objective: We investigated ECP levels in nasal secretions (NS) of healthy volunteers obtained by seven different methods of sample collection to define norm values and to evaluate the clinical use of the different methods.
Methods: A total of 839 healthy individuals were evaluated using blowing the nose (Bl: n = 82), suction (Suc: n = 69), Okuda microsuction technique (MSuc: n = 93), absorbent cotton wool samplers (CWS: n = 156), rubber-foam samplers (RFS: n = 193), nasal lavage (Lav: n = 112) and nasal spray washing (NSW: n = 134).
Results: Missing values occurred in more than 60% in Bl, Suc and MSuc, so that no norm range was defined for these methods. Norm range for ECP in NS was 5-46 ng/mL for CWS, 7-41 ng/mL for RFS, 4-51 ng/mL for NSW, and 3-31 ng/mL for Lav.
Conclusions: When comparing seven different methods used in this study to collect nasal secretions and determine ECP levels, the method based upon absorption or nasal washing was the best.