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.