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 o f nasal lavage. Objective To compare the repeatability and validity of total and differenti al cell counts and eosinophil cationic protein (ECP) in nasal secretions ob tained by two methods of nasal lavage. Patients and methods Twelve healthy subjects and twelve subjects with clini cally 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 sec ond method in the following week. One method was a modification of the meth od 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 coun ts and ECP in normal subjects but better repeatability in subjects with rhi nitis. The modified Greiff/Grunberg method gave higher and more repeatable total cell count and, in subjects with rhinitis, more reproducible ECP leve ls compared with the Naclerio method. Both methods were able to discriminat e between healthy and rhinitic subjects: mean SD eosinophil percentage coun t and eosinophil cationic protein differences were 4.5 +/-4% (P<0.05) and 2 4.5<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), respe ctively, with the Naclerio method. Conclusion Both methods are valid and discriminate between normal and rhini tic subjects. In subjects with rhinitis, although the repeatability of eosi nophil counts is similar by both methods, the modified Greiff/Grunberg meth od gives more reproducible ECP measurements, compared with the Naclerio met hod.