1. The amount of admixture in nasal lavage fluids was determined by addition of 99mTc labelled albumin, providing a correction factor for measurements of cellular material and humoral substances in nasal lavage return as well as a quantitative measure of nasal secretions.
2. Albumin was chosen as marker molecule, since only negligible amounts were absorbed or adsorbed to the mucosa during the nasal lavage.
3. Labelling of the albumin with 99mTc ensured an accuracy of measurements only limited by the precision of the weighing. The isotope allowed for the determination of the amount of admixed secretion to be carried out on the whole sample of lavage fluid, thereby avoiding the necessity of complete admixture between marker and lavage fluid which would be pertinent to marker molecules measured chemically. The radiation from a nasal lavage is minimal and the procedure is fully acceptable for repeated use in humans.
4. The nasal lavage technique adopted allowed the return of 99.2% (median value) of the instilled volume. The area irrigated was visualized on a gamma-camera, and was demonstrated to cover an area larger than the area reached by challenge from a pumpspray, i.e. a large part of the nose, yet not the oropharynx.
5. A dose related increase in nasal secretion harvested by the nasal lavage in 10 persons challenged with histamine chloride could be demonstrated by this technique.
6. It is concluded that the use of 99mTc-albumin in a nasal washing provides a safe, simple and quick method for determination of the admixed nasal secretion with a remarkable degree of accuracy. The method is therefore suggested to improve determinations of admixture in nasal lavage fluid.