OBJECTIVE To analyze the risk factors for the whole blood trough concentration of sirolimus in liver transplant recipients falling out of the target range(4–10 ng·mL⁻¹) and develop a nomogram risk prediction model.

METHODS Clinical data including demographic characteristics, medication regimen, trough concentration, laboratory test results and adverse reactions of liver transplant recipients underwent sirolimus therapeutic drug monitoring(TDM) from December 2023 to August 2025 in Beijing Tsinghua Changgung Hospital were collected. High-performance liquid chromatography-tandem mass spectrometry was used to detect the trough concentrations of sirolimus. The the risk factors of trough concentration falling out of the target range was assessed by Mann-Whitney U test, chi-square test and Lasso regression, and a nomogram risk prediction model was established.

RESULTS A total of 68 patients were included, with 643 times of sirolimus concentrations. The median daily dose of sirolimus was 2 mg, and the median trough concentration in these cases was 4.81 ng·mL⁻¹, ranging from 1.05 ng·mL⁻¹ to 19.86 ng·mL⁻¹. The 349 cases(54.28%) were within the target range(4 to 10 ng·mL⁻¹). The results of Lasso regression analysis showed that dose, body weight, hemoglobin, total plasma protein and estimated glomerular filtration rate were independent predictors for off-target sirolimus trough concentrations. The nomogram model was constructed based on these variables with area under the receiver operating characteristic curves of 0.66, 0.75 for internal and external validation, with good discrimination.

CONCLUSION The proportion of sirolimus trough concentrations achieving target range in liver transplant recipients is relatively low, suggesting a need for routine TDM. The nomogram model based on Lasso-logistic regression has good prediction efficiency, which is helpful to identify the off-target risk of sirolimus trough concentrations in liver transplant recipients.