Nasal lavage method in the monitoring of upper airway inflammation: seasonal and individual variation.

A noninvasive and reliable method is needed to investigate causal relationship between exposure to bioaerosols in occupational and indoor environments and adverse health effects. As an essential part of the method development, the individual variation as well as seasonal and gender differences in the concentrations of inflammatory mediators in nasal lavage (NAL) fluid were studied. NAL was performed in 10 healthy volunteers every other week for a year. Concentrations of nitric oxide, assessed as nitrite, interleukin (IL)-1 beta, IL-4, IL-5, IL-6, and tumor necrosis factor alpha (TNF alpha) in NAL fluid were measured. The NAL sampling was minimally invasive and well tolerated and no side effects were observed among the studied subjects. Low concentrations of nitrite, TNFalpha, IL-1 beta, IL-4, and IL-6 were detected in the NAL samples of the studied subjects. Within-subject variation in the concentrations of inflammatory mediators in the NAL fluid was at its lowest during the wintertime. Moreover, differences between individuals and genders were statistically significant. In summary, the individual variation in the basal levels of measured inflammatory markers is low, whereas differences between individuals are considerable. Thus, in the studies evaluating upper airway effects of occupational or environmental exposure, the method is most suitable in settings where comparison can be made using test subjects as their own controls.