Chronic rhinosinusitis (CRS) is one of the most common inflammatory chronic conditions, leading to a persistent nasal congestion, nasal discharge, and a loss of smell. Despite sinus surgery and frequent use of oral corticosteroids, a large proportion of individuals with CRS are difficult to treat and have recurrent inflammation. They are usually referred to as individuals with recalcitrant disease and having recurrent nasal polyps (NPs; CRSwNP). The disease poses a significant impact on the patients' health-related quality of life (HrQoL), mainly because of a complete loss of smell. Pharmacological treatment with biological therapies has recently been developed, targeting mediators of the type 2 inflammatory response. However, not everyone benefits from the biological therapy, and it has proven difficult to identify and characterise patients that are responsive to these new medications. Eicosanoids, being arachidonic acid derived bioactive lipid mediators, has been shown to be implicated in CRSwNP. Although there is a clear link between an imbalanced biosynthesis of pro- and anti-inflammatory eicosanoids and type 2 inflammation, to date research has not focused on them as biomarkers in CRSwNP.

The overall aim of this thesis was to explore the potential role of eicosanoids as biomarkers and characterise changes over time in HrQoL as well as the degree of smell loss in patients with severe recalcitrant CRSwNP. The project involved immunoassay analysis of levels of various inflammatory mediators, including a selection of eicosanoids, in nasal tissue, nasal secretions and urine from patients with CRSwNP as well as gene expression analyses regarding biosynthetic enzymes and receptors for eicosanoids in nasal tissues. HrQoL was assessed with SNOT-22 and RAND-36, along with point-of-care tests as eosinophil blood count, fractional exhaled nitric oxide (FeNO) and smell tests with Burghart Sniffin’ Sticks.

Levels of eicosanoids in nasal secretions were found to associate with the disease severity, defined as the extent of NP growth (paper I). One of the eicosanoids, leukotriene E4 (LTE4), were correlated to the degree of smell loss (paper I). An increase in LTE4 between six and 12 months after surgery was demonstrated in patients with recurrent NPs (paper II). Recurrent NPs were identified endoscopically 12 months after surgery and a distinct eicosanoid profile involving LTE4, prostaglandin D2 and 15(S) hydroxyeicosatetraenoic acid was found to be more common in those with recurrence (paper II). A similar eicosanoid profile, based on measurements from nasal tissue samples instead, was also associated with NP recurrence (paper III).

Levels of eicosanoids in nasal tissue and nasal secretions were correlated suggesting that analysis of biomarkers in nasal secretions reflects release from the nasal tissue (paper III). Patients with recurrent NPs had elevated blood eosinophil counts before their surgery, and their sense of smell was significantly impaired both before and after (paper IV). This finding suggests that loss of smell may be the first symptom during recurrence. Although measures of HrQoL could not distinguish patients with recurrent NPs, there was a strong correlation to the degree of smell loss suggesting that loss of smell has a significant impact on the HrQoL (paper IV).

In summary, the results from this thesis contribute to an extended knowledge regarding characteristics relevant for identifying severe recalcitrant CRSwNP. Characteristics of interest included a distinct eicosanoid profile, severe loss of smell and eosinophil involvement, all of which may be possible prognostic markers for severe recalcitrant CRSwNP with rapid NP growth. It may be concluded that such biomarkers can guide the choice of treatment for these severely ill patients – repeated surgery or pharmacological treatment with the newly developed biological therapies.

BACKGROUND: Altered biosynthesis of eicosanoids is linked to type 2 inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP), but their role in recalcitrant NPs is unclear.

OBJECTIVES: We sought to identify endotypes that are linked to recalcitrant CRSwNP, based on eicosanoids, their biosynthetic enzymes, and receptors as well as cytokines and the presence of eosinophils and mast cells in recurrent NPs.

METHODS: Mucosal tissue collected at the time of sinus surgery from 54 patients with CRSwNP and 12 non-CRS controls were analysed for leukotriene (LT) E4, prostaglandin (PG) D2, 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE) and 17 cytokines with ELISAs and Bio-Plex immunoassays. Patient subgroups were identified by cluster analysis and the probability of NP recurrence were tested with logistic regression analyses. Gene expressions were analysed with qPCR. Tryptase and eosinophil-derived neurotoxin (EDN) were measured with ELISAs as indications of the presence of mast cells and eosinophils, respectively.

RESULTS: Clustering of patients showed that an inflammatory signature characterised by elevated LTE₄, PGD₂, 15(S)-HETE and IL-13 was associated with NP recurrence. Previous NP surgery as well as aspirin-exacerbated respiratory disease were significantly more common among these patients. Expression of cyclooxygenase 1 was the only gene associated with NP recurrence. Levels of EDN, but not tryptase, were significantly higher in patients with recurrent NPs.

CONCLUSION: Distinguishing endotypes that include LTE₄, PGD₂, 15HETE and conventional biomarkers of type 2 inflammation could help predict recurrent nasal polyposis and thus identify cases of recalcitrant CRSwNP.

BACKGROUND: Although altered eicosanoid levels are related to disease severity in chronic rhinosinusitis with nasal polyps (CRSwNP), identifying patients prone to recurrent NPs is still difficult. We investigated levels of nasally secreted eicosanoids before and after NP surgery in patients with or without NP recurrence and explored potential endotypes based on pre-surgical eicosanoid levels.

METHODS: Levels of leukotriene (LT) E₄ , LTB₄ , prostaglandin (PG) D₂ , PGE₂ and 15(S) hydroxyeicosatetraenoic acid (15(S)-HETE) were measured in nasal secretions with specific immunoassays at pre-surgery (n = 38) and six- and 12-months post-surgery (n = 35) where NP recurrence was identified endoscopically. Pre- and post-surgical levels were compared between patients with and without NP recurrence. Eicosanoid patterns among patients were explored with cluster analysis and evaluated with clinical parameters.

RESULTS: Patients with recurrent NPs had pronounced pre-surgical levels of nasal 15(S)-HETE, PGD₂ and LTE₄ . From pre-surgery to 12-months after, NP recurrence was associated with significant decrease of 15(S)-HETE and PGD₂ relative to non-recurrence whereas levels of LTE₄ decreased at six-months but increased again at 12-months. Clustering revealed three potential endotypes. Cluster 1 and 3 featured high and low eicosanoid levels, respectively. Cluster 2 had higher levels of LTE₄ and PGD₂ , lower levels of PGE₂ and LTB₄ , and more cases of recurrent NPs and previous NP surgeries.

CONCLUSION: Elevated nasal LTE₄ , 12-month post-surgery, in NP recurrent subjects suggests that postoperative LTE₄ measurements may indicate rapid NP regrowth. A distinct nasal eicosanoid profile may be used for the identification of the most severe recalcitrant patients in need of targeted immunomodulatory therapies. This article is protected by copyright. All rights reserved.

Severe nasal polyposis and mucosal inflammation, in patients with chronic rhinosinusitis (CRS) may include a dysregulated eicosanoid profile, but a clinical role for eicosanoids in CRS with nasal polyps (NP; CRSwNP) remains to be elucidated. This study focused on assessing levels and clinical implications of inflammatory mediators in nasal secretions and urine from patients with different NP severity or Aspirin Exacerbated Respiratory Disease (AERD). Levels of leukotrienes E₄ and B₄, prostaglandins D₂ and E₂ as well as 15(S)-hydroxyeicosatetraenoic acid were measured with enzyme immunoassays and cytokines with magnetic bead immunoassays. Patients with CRSwNP were subdivided based on NP score; CRSwNP-low (NP score ≤ 4, n = 11) or CRSwNP-high (NP score ≥ 5, n = 32) and compared to CRS without polyps (CRSsNP, n = 12), CRSwNP-AERD (n = 11) and individuals without CRS (n = 25). Smell test score, fractional exhaled nitric oxide (FeNO), blood eosinophils and Sinonasal outcome test-22 were assessed as clinical markers. Leukotriene E₄, prostaglandin D₂ and 15(S)-hydroxyeicosatetraenoic acid in nasal secretions correlated with NP score. Nasal leukotriene E₄ also correlated with FeNO and smell test score, with highest levels found in CRSwNP-AERD. Levels of prostaglandin D₂ in nasal secretion as well as urinary levels of the prostaglandin D₂ metabolite 11β-prostaglandin F_2α differed between CRSNP-high and CRSwNP-low. Urinary 11β-prostaglandin F_2α was associated with asthma comorbidity whereas a similar association with prostaglandin D₂ in nasal secretions was not observed. In conclusion, subdividing patients based on NP severity in combination with analysis of eicosanoids in non-invasively collected nasal secretions, may have clinical implications when assessing CRS disease severity.

Objectives: Previous studies have shown that hot saline solution (HSS) nasal irrigation is effective against nasal bleeding and is used to treat nasal hemorrhage. In a pilot study, we evaluated hot saline nasal irrigation in comparison to a routinely used nasal packing in terms of self-reported complications and mucosal healing after functional endoscopic sinus surgery.

Methods: Patients undergoing surgery for bilateral chronic rhinosinusitis received polyvinyl acetate (PVA) nasal packing in the left nostril, and the right nostril was rinsed with 47°C sterile saline immediately after surgery. Patients' experiences of pain, bleeding, and other types of uncomfortable experiences were measured using a visual analog scale for each nostril before, during, and immediately after nasal packing removal. Two weeks post-surgery, the assessments were repeated including an endoscopic evaluation of the mucosa by the surgeon.

Results: Twenty-seven patients completed the study. Prior to removal of the packing, the patients experienced significantly more pain and other uncomfortable experiences in the nostril treated with nasal packing, as compared to the nostril solely rinsed with hot saline. After removal, patients reported significantly more uncomfortable experiences from the packing treated nostril. Two weeks post-surgery, no difference in mucosal healing was observed between the two nostrils.

Conclusions: The results from this study indicate that irrigation with HSS could be an alternative postoperative treatment to conventional PVA nasal packing. Hot saline irrigation may contribute to patients experiencing improved control of postoperative bleeding, pain, and less suffering of other causes as well as health-economic benefits, without affecting the mucosal healing up to 2 weeks post-surgery.

Level of Evidence: 1b.