Evaluation of nasal IgA secretion in normal subjects by nasal spray and aspiration

Nasal washing (NW) is a popular method for collecting human nasal lavage fluid. However, for NW the subject must be trained, and the method is unsuitable for field studies on untrained subjects. To overcome this problem, we have developed an easy and painless method, a nasal spray and aspiration (NSA) method.

This method is different from NW in that the nasal cavity is misted over with saline, and the nasal lavage fluid is aspirated from the nostrils through a silicon tube. First, nasal lavage fluid was obtained twice by NSA with an interval of a week between lavages to evaluate intraindividual variability, and the IgA and protein levels in the nasal lavage fluid were measured by enzyme-linked immunosorbent assay and bicinchoninic acid assay, respectively. Next, the IgA value determined by NSA was compared with that by NW in another 12 normal subjects 2 days after NSA.

In 10 normal subjects, mean volume of saline sprayed into the nose was 0.46+/-0.15 ml (mean+/-S.D.). Mean volume of aspirated nasal lavage fluid containing both sprayed saline and nasal secretion was 0.44+/-0.37 ml. The mean IgA level/mg protein in the nasal lavage fluid determined by NSA was 112+/-18 microg/mg protein at the first and 99+/-20 at the second times of measurement, being highly reproducible. The mean value by NSA was 114+/-19 microg/mg protein, being almost the same as that by NW of 99+/-27.

These findings suggest that the IgA level/mg protein in nasal lavage fluid determined by NSA instead of NW might be useful for assessing the variability of nasal IgA secretion.