Therapeutic drug monitoring of antiretroviral drugs at home using dried blood spots: a proof-of-concept study.

BACKGROUND: In HIV-infected patients, therapeutic drug monitoring (TDM) of antiretroviral drugs is recommended in special populations and in specific situations to optimize therapy. Currently, TDM is performed via measurement of drug plasma concentrations; however, dried blood spots (DBS) may offer a patient friendly and cost-effective alternative. Therefore, this proof-of-concept study assessed the feasibility of TDM of antiretroviral drugs using DBS with sampling at home. METHODS: Included patients were instructed to sample three DBS just before drug intake at three consecutive days at home and one DBS sample together with their routine venous sampling. All samples were analysed using liquid chromatography coupled to tandem mass spectrometry. Feasibility was investigated with a questionnaire and via determination of the calculated plasma trough concentrations. RESULTS: In total, 50 patients (48 male, mean age 50 years [range 29-69]) have been included, of whom most were virologically and immunologically well-controlled. In total, 200 DBS were collected, of which 87.5% were suitable for analysis. The questionnaire showed that most patients (68%) successfully obtained their first DBS and 51% preferred DBS over plasma sampling. Plasma trough concentrations could adequately be determined from DBS. CONCLUSIONS: This proof-of-concept study confirms the feasibility of TDM of antiretroviral drugs using DBS with sampling at home, thereby opening the possibility to obtain trough concentrations at home in populations where venous sampling is difficult.