Statistical analysis
REGRESSION
Quantitative variables were presented as median with interquartile range (IQR). Comparisons of the biochemical liver tests at baseline, 1-, 3-, 6-, or 12 months were performed using the Wilcoxon signed-rank test for paired data. Categorical variables were presented as counts with percentages and compared by Chi-squared test or Fisher’s exact test. Adverse outcome-free survival was estimated using the Kaplan–Meier method and compared by log-rank test. The effect of baseline variables or 1-, 3-, 6-, or 12 month biochemical response to UDCA on survival was estimated using the Cox proportional-hazards regression model. The average hazard ratio (HR) and 95% confidence interval (CI) were used to quantify the strength of the statistical links between the tested variables and survival. Univariate Cox regression analyses were applied to the training cohort to identify prognostic factors with different cut-off values of liver tests.The C-index, likelihood ratio Chi-square, area under time-dependent receiving operator characteristic (timeROC) curve, sensitivity, specificity, positive (PPV), and negative (NPV) predictive values, as well as positive (PLR) and negative (NLR) likelihood ratios, were calculated for all definitions to assess their performance in predicting long-term outcomes. Akaike information criterion (AIC) was also calculated to compare the loss of information for different models. Bootstrapping with 1,000 samples was used for model validation. C-index and 95% CI was calculated by survcomp package by in R software. Statistical analyses were carried out using SPSS software (version 22.0; SPSS Inc., Chicago, IL, USA). The survival curve was plotted using the R 3.5.2 software with survival, and rms packages. The timeROC curve was plotted by timeROC package. All analyses were two-sided and 