Statistical analysis
inferior turbinate reduction, airway blockage, enlargement of the inferior turbinate
REGRESSION, SECONDARY, RECRUITMENT
Analyses were performed according to a predetermined analysis plan.The planned population defining analyses included an ITT analysis, a per protocol analysis, and a per treatment analysis.


We explored the impact of the recruitment site on the primary outcome analysis by inserting the centre as a random effect with the mixed effect model.Analyses of the secondary outcome measures followed the same primary multiple linear regression modelling. Although inferior turbinate reduction was not a randomised intervention, its effect on the primary outcome was explored as a planned covariate in the linear regression model.Further planned multivariable linear regression sensitivity of the ITT analyses considered adjustment for other important baseline factors in the regression model. To utilise the full information from the continuous measure, model 2 adjusted for continuous baseline score on the NOSE scale rather than the three categories used at baseline. Model 3 included age, ethnicity, recruitment site (as a random effect), smoking history, double ordinal airway subjective scale, endoscopy findings (location of deviation, severity of airway blockage, and enlargement of the inferior turbinate), and four nasal patency variables. These variables were initially regressed univariately against the primary outcome measure to screen for independent relatedness. Any variable with P>0.1 was included for consideration in further modelling based on forward selection. Non-linear continuous covariates were considered for fractional polynomial transformations, if appropriate.The importance of baseline severity within the ITT population, as a continuous distribution of score on the NOSE scale at randomisation, was further explored graphically using a subpopulation treatment effect pattern plot (STEPP) analysis.All data were analysed using STATA, version 16.