Development and validation of limited sampling strategy equation for mycophenolate mofetil in children with systemic lupus erythematosus

The aim of this study was to establish a limited sample strategy (LSS) to predict the mycophenolic acid (MPA) area under the curve (AUC)((0-12)) in children with systemic lupus erythematosus (SLE). Three months after initiation of mycophenolate mofetil (MMF) 26 children with SLE presented for therapeutic drug monitoring of MPA. On the day of the test, 10 specimens were collected, analyzed, and MPA AUC((0-12)) was calculated. Using step-wise regression analysis, LSS equations were developed. Using bootstrap validation, the predictive performance was calculated. The measured mean (standard deviation) for the trough concentration and AUC((0-12)) were 2.55 (1.57) μg/ml and 62.6 (21.67) mg.h/L, respectively. The range of trough concentrations and AUC((0-12)) were 0.7–5.54 μg/ml and 22.1–104.8 mg.h/L, respectively. The interindividual variability (%CV) for dose normalized AUC((0-12)) and dose normalized C(trough) was 46.5% and 61.1%, respectively. The correlation between the concentrations at the different time points and MPA AUC((0-12)) ranged from 0.05 (1.5 h) to 0.56 (4 h). Two LSS equations that included 4 or 5 time points up to 3 h were developed and validated. The 4 point LSS had a correlation (R(2)) of 0.88 and the 5 point LSS an R(2) of 0.87. With respect to the 4 point and 5 point MPA LSS AUC((0-12)), the bias was 1.92% and 1.96%, respectively, and the imprecision was 11.24% and 11.28%, respectively. A 4 point LSS which concludes within 3 h after the administration of the MMF dose was developed and validated, to determine the MPA AUC((0-12)) in children with SLE.