2.2 Statistical analysis
Statistical analyses were conducted using Stata v.16.1 software (Stata Corporation LLC, College Station, USA). Categorical variables were presented as counts and percentages, and were analyzed using either the chi-square or Fisher’s exact test. Continuous variables were presented as means with standard deviations (SD) or medians with interquartile ranges (IQR), and comparative analyses were performed using either Student’s T-test or the Mann–Whitney U test. Univariable and multivariable logistic regression analyses were employed to identify factors independently associated with R/R HLH. The results were presented as odds ratios (OR) and 95% confidence intervals (CI). Receiver operating characteristic (ROC) curve analysis was applied to determine the optimal cutoff for predicting R/R HLH. Kaplan-Meier survival analysis and the Log-rank test were utilized to evaluate the 2-year and 5-year overall survival (OS) rates. A p-value of less than 0.05 was considered statistically significant.