2.1 Design, setting, and participants
A cross-sectional study of CRS patients undergoing ESS was conducted. CRS patients were recruited from ”Blinded for review” according to a protocol approved by the Institutional Review Board of ”Blinded for review” (ethics approval number 25-36) as described previously11. Informed consent was obtained from all participants. All experiments were conducted according to the Declaration of Helsinki on biomedical research involving human subjects. Sinonasal tissues, such as uncinate tissues and nasal polyps, were obtained during ESS, and peripheral blood samples were collected preoperatively (the day before ESS) and postoperatively. The diagnosis of CRS was made based on clinical, endoscopic, and radiographic criteria as described in the European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS) 20201. A detailed list of the patient characteristics is presented in Table 1. The CRS cases were classified as eCRS or non-eCRS according to a published clinical scoring system (JESREC score)5. The JESREC score was calculated with the following point breakdown: bilateral disease sites (3 points); nasal polyps (2 points); CT shadow, ethmoid > maxillary sinus (2 points); and blood eosinophilia, 2% to 5% (4 points), 5% to 10% (8 points), or more than 10% (10 points). Patients with scores higher than 11 points and mucosal eosinophilia higher than 70 per high-power field were defined as eCRS patients. Conservative medical treatments and nasal saline irrigations had previously failed in all CRS patients. The patients were not treated with systemic corticosteroids (SCS) within 4 weeks before the surgery. Patients for whom postoperative blood samples were unavailable were excluded from the study.