2.5 Statistical analysis
The statistical software SPSS 20.0 was used for statistical analyses. The χ2 test was used for univariate analysis. Multivariate logistic regression analysis was used for multivariate analysis. According to the results of the univariate and multivariate analyses, characteristics with statistically significant differences were compiled to establish the LFS system. The best critical score was determined in combination with the receiver operating characteristic (ROC) curve and clinical practice. The kappa statistic was calculated to evaluate the reading consistency between the two laryngologists (kappa <0.2 indicates poor consistency; 0.2–0.4, fair consistency; 0.4–0.6, moderate consistency; 0.6–0.8, relatively strong consistency; and 0.8–1.0, very strong consistency). Differences were considered statistically significant at P < 0.05.