Optimizing protein harvest from nasal brushings for determining local allergy responses

Background: Rhinitis is a highly prevalent yet often misdiagnosed condition. Patients who have local allergic rhinitis are regularly mislabeled as having a nonallergic etiology. Thus, a highly accurate, reproducible, and noninvasive assessment, which can be performed quickly and with minimal discomfort to the patient, is required. Objective: The aim of this research was to identify the efficiency of various nasal brushes as tools for harvest and collection of epithelial proteins and its suitability for identification of rhinitis. Methods: Nasal epithelial mucosa samples were taken from patients undergoing turbinate surgery using a cytology brush, a dental brush, and a nasal curette in random order. After washing in phosphate-buffered saline, the suspended cells were sonicated. Total protein content was assessed for all samples by bicinchoninic acid assay measured using a Nanodrop machine. Identification of nasal-specific immunoglobulin E (spIgE) was then assessed using immunoassay and compared to the patient’s allergic status from epicutaneous and serum testing. The lower threshold limit for the spIgE in nasal brushings was determined using the results of serum spIgE tests as the reference. The diagnostic accuracy of this new established cutoff value was determined. Results: The cytology brush was found to be the optimal tool for maximal nasal mucosa protein collection followed by dental brush and nasal curette (0.75 ± 0.45 mg/mL vs 0.43 ± 0.24 mg/mL vs 0.071 ± 0.55 mg/mL, respectively; P <.01). The optimal cutoff value of nasal spIgE from the cytology nasal brushings was 0.14 kUA/L to predict allergic status from serum testing. This gave a sensitivity of 75%, specificity of 86%, positive predictive value of 74%, likelihood ration positive of 5.40, and diagnostic odds ratio of 18.62. Conclusion: The cytology brush is the optimal tool for protein collection. This is an easy and direct method to sample the nasal mucosa for assessment of nasal allergy or future biomarkers.