Vancomycin and creatinine determination in dried blood spots: Analytical validation and clinical assessment

This study aims to develop a liquid chromatography tandem-mass spectrometry (LC-MS/MS) method for vancomycin and creatinine measurement in dried blood spots (DBS) and to evaluate its clinical application. The analytes were extracted from DBS and analyzed by LC-MS/MS. Vancomycin and creatinine DBS and plasma concentrations were compared in 54 and 35 samples, respectively, from 29 patients. Accuracy was 94.4–102.6%, intra-assay precision was 2.1–5.6%, and inter-assay precision was 3.5–7.0%. Patients vancomycin plasma to DBS concentration ratios were highly variable (1.148–5.022), differently from creatinine (0.800–1.283). The assay has adequate analytical performance. Plasma concentrations can be satisfactorily predicted from DBS measurements for creatinine, but not for vancomycin, which limits its clinical application.