[Usefulness of the urea method in nasal discharge analysis]

We examined urea used as a dilution marker of broncho-alveolar lavage fluid to determine whether it was also useful as a dilution marker of nasal lavage fluid. We measured the concentration of urea in nasal secretions and peripheral blood for 91 cases. As a comparison, we also measured the total protein and albumin in nasal secretions and peripheral blood. The urea concentrations in nasal secretions were strongly correlated with that in peripheral blood (coefficient of correlation 0.925). The urea concentration in nasal secretions was approximately 2.4 times higher than the level in peripheral blood. No correlation was observed between total protein or albumin levels in nasal secretions and those in peripheral blood. In two patients with Japanese cedar pollinosis, we measured histamine concentration in nasal lavage fluid. Although no change in histamine concentration was observed by direct measurement, after the values were corrected for urea level, an increase in histamine was clearly observed during the cedar pollen season. The urea method was found to be useful as a dilution marker for nasal lavage fluid.