Background: Several objective methods are used to assess the result of nasal allergen challenge.

Objective: The aim of this study was to compare the diagnostic value of nasal nitric oxide (nNO) measurements with that of peak nasal inspiratory flow (PNIF), nasal lavage fluid ß-tryptase levels, and changes in cell count after nasal challenge with grass pollen.
Methods: The study population comprised 24 patients allergic to grass pollen and 24 healthy controls. All participants underwent grass allergen challenge preceded by administration of placebo. A visual analog scale was administered. nNO and PNIF were determined, and nasal lavage fluid was collected before and 30 minutes after administration of placebo and allergen. The study was performed outside
the pollen season.

Results: Significant changes in nNO, PNIF, nasal lavage fluid ß-tryptase level, and cell count were observed only in allergic patients after administration of the allergen. Receiver operating characteristic (ROC) curves were drawn for each determination. A change in nNO levels of –11.987% was indicated as the best cutoff point for differentiating between allergic patients and healthy participants with a sensitivity of 60.9%, specificity of 100%, negative predictive value of 71%, and positive predictive value of 100%. Comparison of the area under the ROC curve did not show signifi cant differences between the diagnostic value of changes in nNO levels and other objective methods of assessing the outcome of the challenge.

Conclusion: Changes in nNO levels do not differ significantly from other methods used to objectively assess the outcome of nasal challenge. Given their insufficient sensitivity, nNO measurements have limited value as the sole diagnostic tool when assessing the outcome of nasal challenge.

Key words: Nasal nitric oxide. Nasal allergen challenge. Allergic rhinitis.