Repeatability and validity of cell and fluid-phase measurements in nasal fluid: a comparison of two methods of nasal lavage

Background There is little information on the repeatability of cell counts and fluid-phase measurements in nasal fluid obtained by different methods of nasal lavage. Objective To compare the repeatability and validity of total and differential cell counts and eosinophil cationic protein (ECP) in nasal secretions obtained by two methods of nasal lavage. Patients and methods Twelve healthy subjects and twelve subjects with clinically stable allergic rhinitis were randomly assigned to two nasal lavages (separated by 48 h), by one of two methods in the first week and by the second method in the following week. One method was a modification of the method described by Greiff et al. and Grunberg and coworkers and the other was that described by Naclerio and coworkers. Results Both methods of nasal lavage gave poorly repeatable eosinophil counts and ECP in normal subjects but better repeatability in subjects with rhinitis. The modified Greiff/Grunberg method gave higher and more repeatable total cell count and, in subjects with rhinitis, more reproducible ECP levels compared with the Naclerio method. Both methods were able to discriminate between healthy and rhinitic subjects: mean SD eosinophil percentage count and eosinophil cationic protein differences were 4.5 +/-4% (P<0.05) and 24.5<plus/minus>46.9 mug/L (P<0.05), respectively, with the modified method and 7.0<plus/minus>4% (P<0.05) and 26.9<plus/minus>68 mug/L (P<0.05), respectively, with the Naclerio method. Conclusion Both methods are valid and discriminate between normal and rhinitic subjects. In subjects with rhinitis, although the repeatability of eosinophil counts is similar by both methods, the modified Greiff/Grunberg method gives more reproducible ECP measurements, compared with the Naclerio method.