Sample size estimation and statistical analysis
SECONDARY
Power Analysis and Sample Size (PASS) version 11 was used for sample size estimation. The sample size was determined based on data from a meta-analysis involving 25,000 patients, which claimed an overall specimen adequacy rate of 87.1% for thyroid FNA (For a patient with more than one nodule undergoing FNA, the nodules were considered independent observations for statistical analysis. Continuous variables were expressed as means and standard deviations. Categorical variables were expressed as frequencies and percentages. The primary outcome was analyzed using Wald test. The difference between the adequacy of the two methods was expressed as a two-sided 95% confidence interval (CI). The S- method was considered non-inferior to the S+ method if the lower bound of the two-sided 95% (equivalent to one-sided 97.5%) CI of the difference in specimen adequacy (S- minus S+) was greater than -10%. Chi-square tests were used to analyze the secondary outcomes. Statistical Package for Social Sciences (SPSS) version 23 and Statistical Analysis System (SAS) version 9.4 were used for all analyses.