Monitoring of Adalimumab Concentrations at Home in Patients with Inflammatory Bowel Disease Using Dried Blood Samples

BACKGROUND: Adalimumab (ADL) is a subcutaneously administered anti-tumor necrosis factor (TNF) agent used in the treatment of patients with inflammatory bowel disease. Higher ADL trough concentrations are associated with improved clinical and endoscopic outcomes. Therapeutic drug monitoring (TDM) of ADL might be facilitated by using dried blood samples (DBSs) from capillary blood obtained at home. The study aimed to compare serum ADL concentrations obtained through venipuncture to ADL concentrations in DBSs. METHODS: Patients with Crohn's disease and ulcerative colitis receiving induction or maintenance ADL therapy were enrolled in this prospective cohort study. Blood was obtained through venipuncture and through DBSs during a regular outpatient visit (time point 1). Just before the next ADL administration, patients performed DBSs at home (time point 2). For this time point, serum ADL concentrations were estimated by Bayesian analysis. RESULTS: Thirty-three patients with inflammatory bowel disease were enrolled. During the outpatient visit, samples were obtained after a median (interquartile range) of 6 (4-10) days after the last ADL dose. A high correlation was found between DBSs and venipuncture results (Pearson correlation: ≥0.96), without any clinically relevant bias. For DBSs performed by patients at home, initial comparison showed a moderate correlation between DBS results and predicted ADL serum concentrations (Pearson correlation: 0.51), although no bias was present. In addition, DBS eluate results compared with predicted ADL serum concentrations showed a mean absolute percentage error (ie, accuracy) of 45%. CONCLUSIONS: High correlations were found between ADL serum concentrations obtained through conventional venipuncture and DBSs, which indicates that this home-based test can facilitate therapeutic drug monitoring-based ADL dose adjustments in daily practice.