Differential nasal swab cytology represents a valuable tool for therapy monitoring but not prediction of therapy response in chronic rhinosinusitis with nasal polyps treated with Dupilumab
Introduction: Chronic Rhinosinusitis with nasal polyps (CRSwNP) is a common
chronic disease with a high impact on patients’ quality of life. If conservative and
surgical guideline treatment cannot sufficiently control disease burden,
biologicals can be considered as a comparably new treatment option that has
revolutionized CRSwNP therapy since the first approval of Dupilumab in 2019.
With the aim to select patients who benefit from this new treatment and to find a
marker for therapy monitoring, we investigated the cellular composition of nasal
mucous membranes and inflammatory cells of patients suffering from CRSwNP
and undergoing Dupilumab therapy using non-invasive nasal swab cytology.
Methods: Twenty CRSwNP patients with the indication for Dupilumab therapy
have been included in this prospective clinical study. In total, five study visits were
conducted with ambulatory nasal differential cytology using nasal swabs starting
with the beginning of therapy and followed by visits every 3 months for 12
months. First, these cytology samples were stained with the May-GrunwaldGiemsa method (MGG) and the percentage of ciliated cells, mucinous cells,
eosinophil cells, neutrophil cells, and lymphocytes was analyzed. Secondly, an
immunocytochemical (ICC) ECP-staining was performed to detect eosinophil
granulocytes. Additionally, during each study visit the nasal polyp score, SNOT20
questionnaire, olfactometry, the total IgE concentration in peripheral blood as
well as the eosinophil cell count in peripheral blood were recorded. The change
of parameters was evaluated over one year and the correlation between clinical
effectiveness and nasal differential cytology was analyzed.
Results: In both MGG (p<0.0001) and ICC analysis (p<0.001) a significant
decrease of eosinophils was seen under Dupilumab treatment. When patients
were divided into a Eo-low- (<21%) and Eo-high- (≥21%) group according to the
percentage eosinophils in nasal swab catology in the first study visit, the Eo-highgroup showed a greater change of eosinophils over time (D17.82) compared to
the Eo-low-group (D10.67) but, however, no better response to therapy. The
polyp score, SNOT20 questionnaire, and total IgE concentration in peripheral
blood showed a significant decrease during the observation period (p<0.0001).
Discussion: Nasal swab cytology as an easy-to-apply diagnostic method allows
detection and quantification of the different cell populations within the nasal
mucosa at a given time. The nasal differential cytology showed a significant
decrease of eosinophils during Dupilumab therapy and can therefore be used as
non-invasvive method for monitoring therapy success of this cost intensive
therapy and potentially can allow an optimized individual therapy planning and
management for CRSwNP patients. Since the validity of initial nasal swab
eosinophil cell count as a predictive biomarker for therapy response was
limited in our study, additional studies including larger number of participants
will be necessary to further evaluate the potential benefits for clinical practice of
this new diagnostic method