[Usefulness of the urea method in nasal discharge analysis]

Area of Science:

• Allergy and immunology
• Respiratory medicine
• Biochemistry

Background:

• Bronchoalveolar lavage fluid (BALF) commonly uses urea as a dilution marker.
• The utility of urea as a nasal lavage fluid (NLF) dilution marker remains underexplored.
• Accurate NLF analysis requires reliable methods for correcting sample dilution.

Purpose of the Study:

• To evaluate urea as a dilution marker for nasal lavage fluid.
• To assess the correlation between urea concentrations in nasal secretions and peripheral blood.
• To determine the usefulness of urea correction for analyzing inflammatory markers in NLF.

Main Methods:

• Measured urea, total protein, and albumin concentrations in nasal secretions and peripheral blood from 91 subjects.
• Analyzed the correlation between urea levels in nasal secretions and peripheral blood.
• Measured histamine concentrations in NLF for two patients with Japanese cedar pollinosis, with and without urea correction.

Main Results:

• Nasal secretion urea concentrations showed a strong positive correlation with peripheral blood urea levels (r=0.925).
• Urea levels in nasal secretions were approximately 2.4 times higher than in peripheral blood.
• Total protein and albumin levels in nasal secretions did not correlate with peripheral blood levels.
• Urea correction revealed a significant increase in histamine during Japanese cedar pollinosis season, which was not apparent with direct measurement.

Conclusions:

• Urea is a valuable and reliable dilution marker for nasal lavage fluid.
• Urea correction enhances the accuracy of measuring inflammatory mediators, such as histamine, in NLF.
• This method improves the assessment of allergic responses and other conditions affecting nasal secretions.