2.3. Mucus acquisition and laboratory analysis of inflammatory mediators

At the time of postoperative visit, prepunched 3/8 inch hydroxylated polyvinyl acetate (Medtronic, Inc) sponges were placed in the middle meatus (MM) for mucus collection and kept for 8 min prior to removal. Samples were kept at −80°C prior to and after processing. The polyvinyl alcohol sponges were then centrifuged at 14,000 rpm for 10 min and extracted with a further 100 μl of phosphate‐buffered saline (PBS) and 1% protease inhibitor cocktail to collect nasal secretions. The concentration of eosinophil cationic protein (ECP) in MM mucus was determined by a commercial ELISA kit (MBL, Woburn, MA) following the manufacturer's instructions. The concentrations of IFN‐γ and IL‐17a in MM mucus were measured using EMD Millipore MILLIPLEX MAP human high‐sensitivity T‐cell panel Luminex kits (Burlington, MA) following the manufacturer's recommended protocols. We specifically focused evaluation on these three biomarkers, as they are well characterized to be associated with each of the three endotypes found in CRS. ¹