From venipuncture to self-sampling dried blood spots: a shift in monitoring testosterone levels

Dried blood spot (DBS) sampling enables convenient at-home blood collection, suitable for patients needing regular check-ups, such as those receiving testosterone replacement therapy (TRT). This study assessed the feasibility and reliability of DBS sampling for monitoring testosterone concentrations in patients undergoing TRT, aiming to provide a convenient at-home alternative to venipuncture.

Twenty healthy volunteers (12F/8M) and 56 male patients (n=59 samples) receiving TRT were included. Blood was collected parallel by venipuncture (reference) and patient-performed finger prick (DBS) following instruction materials and additional verbal guidance from the andrology consultant. Feasibility and patients' experience were evaluated through questionnaires. Testosterone concentrations in both serum and DBS were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

In healthy volunteers, serum and DBS testosterone concentrations were highly correlated (y=-0.021 + 0.66x; r=0.99). For patients receiving intramuscular testosterone undecanoate, this correlation was strong (y=1.3 + 0.54x; r=0.87). However, DBS samples from patients using testosterone gel showed extremely elevated testosterone levels compared to serum, likely due to local contamination. Most healthy volunteers and in general all patients preferred at-home DBS-sampling over venipuncture at the hospital when regular check-ups are necessary, citing convenience and reduced travel time.

At-home DBS sampling is a feasible and reliable method for monitoring testosterone in patients treated with intramuscular testosterone undecanoate, improving patient comfort and convenience. However, DBS sampling at-home is currently unsuitable for patients using testosterone gel, likely due to contamination issues. Comprehensive patient education on collection of DBS samples is crucial to ensure high-quality DBS and accurate testosterone quantification.