Real‐world evaluation of capillary microsampling for drug monitoring of anti‐seizure medications

Objective Capillary microsampling offers a minimally invasive alternative to venipuncture for therapeutic drug monitoring (TDM) of anti‐seizure medications (ASMs). We evaluated the feasibility and reliability of volumetric absorptive microsampling (VAMS) and quantitative dried blood spot (qDBS) devices for ambulatory self‐collection and at‐home use in persons with epilepsy (PwE). Methods PwE attending the Epilepsy Centre of the IRCCS‐Istituto delle Scienze Neurologiche di Bologna (Italy) were enrolled between October 2023 and October 2024. Participants performed supervised self‐collection using VAMS and qDBS in ambulatory setting and at‐home self‐collection with VAMS devices. Sample quality, delivery success, and patient‐reported outcomes (ease, pain, and clarity of instructions) were recorded. Carbamazepine, lacosamide, lamotrigine, and levetiracetam were quantified using a validated ultra‐high performance liquid chromatography‐tandem mass spectrometry (UHPLC–MS/MS) method. Reliability was assessed by comparing at‐home VAMS with ambulatory VAMS and cross‐validating qDBS with VAMS and venous plasma samples using Bland–Altman analysis and linear regression. Results A total of 105 PwE (66% female, mean age 41 years) performed at‐home and ambulatory self‐collection using VAMS and qDBS devices. Most at‐home VAMS samples (88%) were received by the laboratory within 7 days, and 86.8% met high‐quality criteria. For lacosamide, lamotrigine, and levetiracetam, we found strong correlations between at‐home and ambulatory VAMS (Pearson's r ranging from .88 to .98) and low mean bias (<1.0 μg/mL). Conversely, carbamazepine showed lower reliability ( r = .31; p = .49; bias = 2.05 μg/mL). Cross‐validation of qDBS vs plasma confirmed good agreement (slope = .92, .63–1.21) with no significant systematic bias. Patient feedback indicated that self‐collection was easy and minimally painful, although age>60 years impacted sampling quality, particularly for qDBS ( p = .04). Significance VAMS‐based self‐collection is feasible and reliable for at‐home TDM, provided that high‐quality sampling is ensured. qDBS represents a reliable alternative for ambulatory monitoring. Future work should focus on optimizing sampling procedures for older adults and improving logistics for home‐based microsampling.