Nasal cytology is a useful diagnostic tool presenting pictorially the current condition of the nasal mucosa in terms of epithelium exfoliation and the inflow of inflammatory cells from the tissue pool1,20,22. The information on the local, mucosal inflammation facilitates making a decision on diagnosis and the proposed treatment in patients with allergological, laryngological or other problems of the respiratory tract. It is expected that the cytogram indicates, whether the cytological picture supports the existing inflammation and what kind of inflammatory cells dominate20.
Referring to the experience of the Centre of Allergology in Kraków in cytological analyzes we have proposed a new coefficient, which may be an initial criterion for the assessment of cytological material, indicating the intensity of inflammation. As it was shown, the ratio between epithelia and inflammatory cells correlates well with the diagnosis of the selected diseases of upper and lower respiratory tract. Considering two major clinical phenotypes of non-infectious rhinitis: allergic rhinitis (AR) and nonallergic rhinitis (NAR)23, NAR, in our study determined as chronic rhinitis, belonging to the nasopharyngitis group, is thought to be closely related to the local, intensive inflammatory process, while AR does not have to be associated with an evident inflow of inflammatory cells, apart from AR provoked by pollen allergens. Discussing the problem of NAR, the authors emphasize, that there is a difference between ICD-10 and ICD-11 classifications, so currently the non-allergic rhinitis is pointed out not in the group of chronic rhinitis, as previously, but in the group of vasomotor and allergic rhinitis and described as an inflammation of nasal mucosa in which allergic mechanisms are not involved and covers many different phenotypes.
We have found, that in about half of the patients with chronic nasopharyngitis, the activity of inflammatory cells is enhanced, while in the rest of patients the persistent inflammation is expected. NAR involves a heterogeneous group of patients suffering from rhinitis without clinical signs of infection and without systemic signs of allergic inflammation, being divided into several sub-groups as follows: drug-induced rhinitis, rhinitis of the elderly, hormonal rhinitis including pregnancy-induced rhinitis, nonallergic occupational rhinitis, gustatory rhinitis, and idiopathic rhinitis15,24.
Some authors stated that the higher inflammatory cells migration could be related to more active exposition to the increasing seasonal allergen concentration in intermittent AR, especially plant pollen, e. g. grasses10 and the decreasing persistent allergen count in persistent AR25,26, provoked by a year-round allergens, e.g. originated from house dust mites16,26,27,28. This observation was confirmed in our study, because when the whole group of patients diagnosed into allergic or vasomotor rhinitis was considered, the less frequent the inflammatory cytograms were obtained. When the diagnoses of allergic and vasomotor rhinitis were analyzed separately, it was clearly stated that among this group of rhinitis, only patients sensitive to pollen allergens manifest the increased influx of migrating cells. Taking into account not only the inflammatory pool cells, but also the relationship between both inflammatory and epithelial cells makes the diagnosis more objective and makes the doctors aware of the depth of the ongoing inflammation. Minimal persistent inflammation, characterized, at nasal cytology, by a presence of neutrophils and a very low ciliated cell expression, was observed in bakers exposed for a long time to flour dust and allowed to diagnose neutrophil, occupational rhinitis29.
An in-depth analysis of the cellular composition of cytograms allows for the assessment of inflammation in the context of specific diseases, considering first of all two types of cellular inflammation, provoked by eosinophils and neutrophils. Eosinophils and mast cells are considered to be the central effector cells in the allergic reaction30, in the case of NAR, and their occurrence is essential for NAR phenotypes differentiation, especially NARES and NARESMA1,31. We have found, that in patients with chronic, non-allergic rhinitis and severe inflammation, the eosinophil-induced response was less pronounced than in patients without intensive inflammatory process, when the other cells contribute to the pathomechanism of reaction.
When AR is assessed by nasal cytology, eosinophils are expected as a predominant cell type, followed by mast cells and basophils32,33. In our previous study, we have documented that the number of patients with eosinophils > 20% in the SPT(+) group was higher in patients with persistent symptoms, while in the SPT(-) group, the number of patients with intermittent symptoms in the subgroup > 20% of eosinophils statistically prevailed (p < 0.001)10. Tissue infiltration by eosinophils occurs mainly during the late phase of IgE-mediated allergic response and results in the release of eosinophil mediators, which in turn injure the nasal epithelial cells and induce nasal hyperresponsiveness to several irritant stimuli, causing delayed allergic symptoms and perpetuating allergic inflammation24.
The increased inflow of eosinophils should be estimated in relation to the intensity of the inflammation process (in our study 11.54% versus 4.89% on average, respectively in Epith:Infl > 1 versus Epith:Infl ≤ 1), even though the other authors reported that the percentage of eosinophils ranges from 20 to 90%1,3. We recommend also taking into account that the value of 20% of eosinophils in all counted cells corresponds to 30–40% of these cells in the group of inflammatory cells in patients with normal cytogram and to around 45% of eosinophils in patients with the evident inflammatory picture, when the current disease advancement is estimated.
It should be expected that in patients with less evident eosinophilic reaction, the neutrophils are responsible for the development of inflammation, in a non-specific reaction. This practical information is useful to interpret cellular profiles, while allergic rhinitis and non-allergic rhinitis are suspected. It must be singled out that it is not possible to clearly classify AR as an eosinophilic response and NAR as taking place only on the basis of the nonspecific reaction with the participation of neutrophils (as suggested by Tulic and Hamid34). Moreover, chronic and/or untreated AR may result in complications, which include recurrent chronic rhinosinusitis and the formation of nasal polyps, although our results do not indicate the evident inflammation picture in the case of rhinosinusitis. There is a large accumulation of eosinophils and their cytokines in both of these cases, attributed to IL-5 and eotaxin, an eosinophil chemo-attractant, the production of which is significantly increased in the nasal mucosa34.
It is worth underlining that patients diagnosed with vasomotor rhinitis as a form of non-allergic inflammation of the nasal mucosa that is characterized by nasal congestion and posterior pharyngeal drainage, present with the cytograms of a less inflammatory design, but the increased eosinophilic reaction (https://icd.who.int/browse11/l-m/en). The pathophysiology of this phenotype is still not fully discovered. Because vasomotor rhinitis, characterized by nasal hyperreactivity, can refer acc. to Gelardi et al. 202235 to both AR and NAR, the occurrence of eosinophils seems to be diagnostically important in patients with excessive reactivity of the nasal mucosa.
The cellular profile of the mucosal inflammation may affect the efficacy of the individualizing of a given patient treatment31,36, which is in line with the precision medicine approach. Meltzer et al.37 assessed the effect of intranasal fluticasone propionate and beclomethasone dipropionate in seasonal and perennial AR, which showed a favorable therapeutic effect—a decrease in the number of eosinophils and basophils, but a relative lack of change in the percentage of neutrophils. Özgür et al.38 used cytology as an objective test of the efficacy of periodic AR treatment with nasal corticosteroid in combination with oral cetirizine, in addition to the subjective symptom scale, reducing the percentage of eosinophils in the mucosa, the number of neutrophils and goblet cells also decreased.
Breaching and penetration of the mucosal barrier is considered crucial for the pathogenesis of chronic rhinosinusitis (CRS), so cytology can help in preliminary differentiation between the types of inflammation. The cells recruited in type 2 (specific for parasites) are mostly eosinophils and mast cells, while neutrophils are more characteristic for types 1 and 3 (specific for viruses and bacteria/fungi, respectively). Patients with type 2 inflammation usually present with a more recalcitrant disease but they may benefit from new therapeutic options including biological treatment (monoclonal antibodies against cytokines)39. However, the presented results do not indicate clearly that when rhinosinusitis is diagnosed, the severe inflammatory picture in the nasal smears is observed. In our study asthma was classified as a disease related to more intense inflammation of the nasal mucosa, which probably resulted from the close connection between AR and atopic asthma, and even LAR seems to have a progressive course and constitute a potential risk factor for asthma15,17,40.
Gelardi et al. (2009)4 proposed to perform nasal cytology as an easy to use diagnostic procedure even for primary care physicians, to indicate, when anti-inflammatory treatments, such as intranasal corticosteroids and subcutaneous or sublingual allergen immunotherapy, are needed to be ordered. The ratio proposed by us can be helpful in the estimation of inflammation in poly- and mono-sensitized patients, defining a distinct AR phenotype as suggested by Gelardi et al.41, who showed a more intense inflammatory infiltrate in poly- than in mono-allergic patients. In some doubtful situations, nasal cytology can be used to assess local response in a challenge test, e. g. indicating patients with LAR formerly defined as nonallergic rhinitis with eosinophilia syndrome (NARES), characterized by large numbers (inconsistently defined as > 5% to > 20%) of eosinophils on nasal smear18.
Nasal cytology may be useful not only in differentiating infectious from non-infectious nasal and/or sinus disease, but also in overlapping (mixed) rhinitis42. For example, neutrophils may be present not only in acute and chronic rhinosinusitis, but also in conjunction with eosinophils in patients with allergic rhinitis who also have an acute infection process. As Gelardi et al.4 suggested, in some patients, clinical symptoms may be result from a different pathomechanism of inflammation, including nonallergic non-infectious rhinitis overlapping AR. It should be stressed, that in patients with less evident eosinophilic reaction, the neutrophils are responsible for the development of inflammation, in a non-specific reaction. When this response is expected, it is useful to interpret cellular profiles, while the allergic rhinitis and non-allergic rhinitis are suspected.
