Explore the correlation between tacrolimus trough concentration (C₀) and clinical efficacy in children with lupus nephritis (LN), and identify key factors affecting the efficacy of tacrolimus treatment in LN patients..

A total of 120 children with LN who took tacrolimus in our hospital from March 2021 to December 2024 and were monitored for blood drug concentration were retrospectively selected. According to the treatment effect, they were divided into effective group (n=78) and ineffective group (n=42). The basic information, laboratory indicators and other data of the children were collected to explore the influencing factors of the efficacy of the children.

The daily dose of tacrolimus, trough concentration C₀, 24 h urinary protein and albumin in the effective group were higher than those in the ineffective group (all P<0.001), while the glomerular filtration rate was significantly lower than that in the ineffective group (P<0.001). After collinearity diagnosis, the indexes were included in Logistic regression analysis. The daily dose of tacrolimus, trough concentration C₀, glomerular filtration rate and albumin were all protective factors affecting the efficacy of children with LN (P<0.05), while 24 h urine protein quantification was a risk factor (P<0.05). The receiver operating characteristic curve was drawn. The AUC of glomerular filtration rate, 24-hour urinary protein quantification, and albumin in predicting the efficacy of children with LN was 0.882 [95% CI: 0.809-0.956], 0.861 [ 95 % CI: 0.790-0.932], 0.897 [95% CI: 0.837-0.956]. The AUC and optimal cut-off value of tacrolimus daily dose and trough concentration C₀ in predicting the efficacy of children with LN were 0.750 [95% CI : 0.649-0.851 ], 1.45 mg and 0.772 [ 95 % CI: 0.691-0.853 ], 4.05 ng·mL^-1.

The trough concentration of tacrolimus (C₀) is significantly correlated with the clinical efficacy of LN in children, and the daily dose and trough concentration C₀ are key factors affecting the efficacy.