2.3. Data analysis
For all descriptive statistics (e.g., baseline clinical and demographic characteristics, 6MMP:6TGN ratios, etc.), categorical variables were summarized as counts and percentages. Continuous variables were summarized as medians with first to third quartiles, or as means with standard deviation, as appropriate.
All inferential statistical testing was two-sided with an alpha level set to 0.05 (P<0.05). A paired t-test was used if the data was normally distributed, and parametric testing was appropriate. If non-parametric testing was appropriate, a Wilcoxon matched-pairs signed rank test was used. For secondary endpoints with categorical or binary variables (e.g., differences in incidence of symptom reduction), a Chi-square test or Fisher’s exact test was used, as appropriate. For paired continuous variables (e.g., before and after allopurinol in the same patient), a paired t-test was used when assumptions for parametric testing were met (i.e., normal distribution of data), while a Wilcoxon matched-pairs signed rank test was used when non-parametric testing was more appropriate. Finally, for non-paired continuous data, a t-test was used when parametric testing was appropriate, and a Mann-Whitney test was used as the non-parametric alternative. All statistical testing was performed in SAS JMP v16 (SAS, Cary, NC), while figures were created using GraphPad Prism v9.5 (GraphPad, San Diego, CA) and using R v4.1.0 (R Foundation for Statistical Computing), RStudio (RStudio), and the ggplot2 package v3.4.2.11