A widely used antibiotic is vancomycin. To ensure adequate exposure to vancomycin, drug doses are adjusted based on whole-blood concentration measurements, a practice known as therapeutic drug monitoring (TDM). The need for TDM of vancomycin is well established, as described in several national and international guidelines, for dose-optimization in order to achieve successful treatment and to prevent toxicity and reduce microbial resistance. A sampling method for TDM that has become more popular over the recent years is dried blood spotting (DBS). DBS is a design of blood sampling consisting of positioning a drop of capillary blood, preferably taken from the finger, on filter paper. Unlike venous blood sampling (the current gold standard for TDM of vancomycin), DBS seems to have advantages for the patient. The finger prick is less invasive than venipuncture. DBS also enables patients to perform one or multiple finger prick(s) themselves, with the possibility to sample at multiple time points. Due to the fact that vancomycin is nephrotoxic, it would be very efficient and convenient to measure creatinine in the same dried blood spot as the vancomycin. This study is a clinical validation study to validate the DBS assay for vancomycin.

Inclusion Criteria:

• Clinical patients
• Aged 18 and over
• Able to understand written information and able to give informed consent
• Treated with vancomycin
• Able and willing to undergo a finger prick for dried blood spot sampling
• Able and willing to fill in a questionnaire

Exclusion Criteria:

• Unable to draw blood samples for study purposes

Hospitalized adults receiving intravenous vancomycin