Nasal Smear as a Modern and Gentle Diagnostic Method for Allergic Rhinitis
Up to 130 million Europeans suffer from allergic rhinitis. Until now, standard diagnostic methods have been skin prick tests and laboratory blood tests. Both methods, however, present significant discomfort for many patients, and skin prick tests can also yield false-positive results. That's why researchers are focusing on new diagnostic possibilities for allergic rhinitis.
Diagnosis of Allergic Rhinitis
Skin prick tests and blood tests to detect specific immunoglobulin E (sIgE) are routine procedures in the diagnosis of allergic rhinitis (AR). The current development of microchip technology allows for the detection of specific IgE and the assessment of antibody concentrations against 112 different allergens from a very small blood sample (30 µl). If specific IgE is not found in the serum despite the presence of allergic rhinitis, a nasal provocation test is performed.
German Study on a New Diagnostic Method
The environmental medicine team at the Technical University of Munich focused on diagnosing AR based on a nasal smear using a method originally intended for blood sample analysis. The aim was to use biochip technology for non-invasive nasal secretion collection and verify whether this technology and procedure can serve as a new diagnostic method for allergic diseases.
German experts tested patients sensitized and non-sensitized to the most common inhalant allergens (dust mites, grass pollens, birch, hazel, and alder). They used molecular diagnostics to determine antibody concentrations in blood and nasal secretion.
Findings
The results of blood tests and nasal smears were very similar. They revealed the same reactions—the body responded with an immune response to the same substances, covering all tested inhalant allergens. The correlation between antibody detection in blood and nasal secretion has been observed in previous studies, but only for certain allergens, and the current findings confirmed a clear positive correlation for a wide range of inhalant allergens.
When comparing statistical indicators of both methods, similar specificity (0.95 for serum examination and 0.96 for nasal smear) and predictive value of the positive test (0.96 for serum and 0.97 for nasal smear) were observed. Sensitivity and predictive value of the negative test were higher for serum diagnostics than for nasal secretion (sensitivity 0.94 vs. 0.85 and predictive value of the negative test 0.92 vs. 0.82).
For sIgE levels against all tested allergens, a significant positive correlation between nasal secretion and serum was found, with the best results achieved for birch pollen, grass, and house dust mites.
Conclusion
The presented study was the first of its kind to systematically evaluate the microchip diagnostic method compared to standard clinical diagnostics. The results may serve as a foundation for developing new diagnostic methods and significantly contribute to the effective determination of a patient's allergic profile. An important benefit of diagnosing allergic rhinitis from nasal secretion is the non-invasive nature of the smear and the comfort it offers compared to blood collection or skin prick tests.
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Sources:
1. Gökkaya M., Schwierzeck V., Thölken K. et al. Nasal specific IgE correlates to serum specific IgE: first steps towards nasal molecular allergy diagnostic. Allergy 2020 Jul; 75 (7): 1802–1805, doi: 10.1111/all.14228.
2. Ives J. Nasal smear as screening test for allergic rhinitis. News-Medical.net, 2020 Apr 17. Available at: www.news-medical.net/news/20200417/Nasal-smear-as-screening-test-for-allergic-rhinitis.aspx
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