Description

The use of vancomycin in OPAT services is widespread, however a drawback of its use is the need for laboratory monitoring of the vancomycin concentration which requires patients to travel to a blood sampling facility or the hospital for blood sampling. At most hospitals at least one or two blood samples per week are obtained for vancomycin drug monitoring from a patient in OPAT service receiving vancomycin. Conventional blood sampling involves an invasive procedure of drawing blood from a vene through a venipuncture, this is performed by a qualified health care worker at a blood drawing facility (often performed by a nurse in the hospital). Besides the burden for the patient to travel to a blood sampling facility the costs also have to be taken into account, contributing to a higher cost for OPAT services.

The hospital pharmacy laboratory of Erasmus University Medical Center has developed and clinically validated a dried blood spot (DBS) assay for measuring vancomycin and creatinine (ADVANCED study). The use of dried blood spot collection to quantify drug concentrations is an innovative technique that requires only a simple finger prick instead of an invasive venipuncture. Consequently, this is less painful and stressful for the patient than conventional blood sampling. DBS can be performed by taking a low-volume finger prick samples (10 to 20 μl) on filter paper. Finger samples can be taken and stored with a desiccant, without the need for processing and freezing of plasma. A small-diameter disc, or chad, can be subsequently punched out from the filter paper, and the drug can be eluted into a liquid matrix prior to a liquid chromatography-mass spectrometry (LC-MS) assay. The main benefit of DBS sampling is that it allows for the ease of self-sampling at home. DBS offers several other practical advantages over conventional plasma sampling. These advantages include lower sample volume requirements, simplified collection techniques, and less restrictive transport and storage conditions.

DBS sampling eliminates the need to travel to a sampling facility as no healthcare professionals are involved in the sampling process. To date, studies investigating the effectiveness of DBS sampling in terms of reducing outpatient visits have not been conducted in the OPAT population. OPAT is provided for patients who are stable and healthy enough to leave the hospital and clinical monitoring of these patient population is minimal. However, clinical monitoring of vancomycin therapy during OPAT is intensive due to TDM of vancomycin. Most protocols oblige at least once weekly TDM of vancomycin, which contributes to outpatient visits. By implementing DBS sampling the investigators hypothesize that the number of outpatient visits regarding vancomycin therapy in OPAT services can be reduced. Furthermore, this effectiveness may increase when a biochemical parameter such as renal function parameter (i.e. creatinine) are measured along with drug concentrations (leading to even less outpatient visits); the benefit of this has not been investigated yet.