Volumetric Microsampling for Patient-Centric Therapeutic Drug Monitoring in Clinical Pharmacology: A Scoping Review

Accurate drug concentration measurement is essential for precision pharmacotherapy, but conventional therapeutic drug monitoring (TDM) requires venous sampling, increasing patient burden, and potentially limiting participation in TDM and model-informed precision dosing (MIPD). Volumetric microsampling enables self-collection of small, fixed volume capillary samples for centralized analysis and may reduce hematocrit-related volumetric bias associated with conventional dried blood spots. This scoping review, conducted according to the PRISMA Extension for Scoping Reviews, synthesized 67 patient-cohort studies published from 2014 through 2026. Studies spanned at least 18 countries and multiple clinical specialties. Liquid chromatography-tandem mass spectrometry was used in 61 studies (91%), and most reported validation using or referencing EMA, FDA, IATDMCT, or CLSI criteria. Recovery was minimally affected across evaluated hematocrit ranges for most analytes, and many analytes remained stable in dried samples, although stability varied by analyte and storage conditions. Where assessed, patient preference was high (80%-100%). However, interpretation against established plasma therapeutic ranges often required whole-blood-to-plasma or capillary-to-venous conversion, with inconsistent derivation and validation methods. Fixed conversion factors performed well for lacosamide and levetiracetam but were less reliable for lamotrigine at high concentrations. Several analyte-matrix combinations, including cefepime, vancomycin, meropenem, paclitaxel, abiraterone, and mitotane, did not consistently meet agreement criteria. Volumetric microsampling can support patient-centered drug monitoring when validated for the specific analyte, matrix, device, and clinical application. Future research should prioritize drug-specific optimization, multicenter validation, standardized conversion reporting, and integration with MIPD platforms.