This study seeks to establish the therapeutic reference range for tacrolimus blood concentrations in pediatric patients diagnosed with Henoch-Schönlein purpura nephritis (HSPN) and to evaluate the factors influencing tacrolimus pharmacokinetics in this population.

Receiver operating characteristic (ROC) curve analysis was utilized to determine the optimal therapeutic threshold for tacrolimus concentration. Comparative analyses were conducted to assess clinical efficacy and adverse event profiles across four groups of tacrolimus concentrations [Group A(< 3 ng·mL ^-1 ), Group B (3- < 5 ng·mL ^-1 ), Group C (5- < 10 ng·mL ^-1 ), and Group D (≥10 ng·mL ^-1 )], thereby establishing a reference therapeutic range. Kaplan-Meier survival analysis was employed to evaluate differences in continuous remission survival rate and remission duration among four distinct concentration groups, validating the precision of the target trough concentration range. Additionally, multivariate linear regression analysis was performed to identify significant factors influencing tacrolimus concentrations.

A cohort of 105 pediatric patients diagnosed with HSPN were enrolled in this study. After six months of tacrolimus therapy, the ROC curve analysis revealed that the tacrolimus trough concentration had significant diagnostic value for clinical efficacy, with an area under the curve (AUC) of 0.816 ( P < 0.01), and an optimal cutoff value of 3.02 ng·mL ^-1 . Comparative analysis of clinical efficacy across four groups demonstrated that Group A exhibited significantly lower efficacy compared to the other groups. After 12 months of tacrolimus treatment, the diagnostic utility of the ROC curve was further confirmed, with an AUC of 0.798 ( P > 0.05), indicating limited predictive performance. Although no significant differences in adverse event rates were observed among the four groups, Group D displayed a notably higher incidence of nephrotoxicity relative to the other groups. Multivariate linear regression analysis identified serum creatinine level as a significant determinant of tacrolimus concentration ( P < 0.05).

In pediatric patients with HSPN in China, maintaining tacrolimus trough concentrations within the therapeutic range of 3–5 ng·mL ^-1 has been demonstrated to achieve optimal therapeutic efficacy.