Stability of acetylsalicylic acid in human blood collected using volumetric absorptive microsampling (VAMS) under various drying conditions

Acetylsalicylic acid (ASA) is one of the most commonly used medications in global market, with a risk of intoxication in certain patients. However, monitoring blood drug concentration often requires frequent hospital visits; hence there is an unmet need to increase patient-centricity by conducting blood sampling at home. Volumetric absorptive microsampling (VAMS) is a device that allows collection of homogenous and accurate volume of blood without venipuncture, and can be utilized by patients who are not in hospital settings; but because ASA is prone to hydrolysis and stabilizing reagents cannot be added to VAMS samples, a way to improve sample stability must be developed. The objective of this study was to identify the cause of instability with ASA samples collected by VAMS, and to evaluate ways to improve sample stability. A liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used for analysis of ASA concentration in whole blood. Samples collected with VAMS were kept under different drying conditions (desiccator, pressurized, nitrogen gas and household vacuum sealer) and were compared to the control samples collected by conventional venous sampling. The recovery of ASA was about 31% of the control when VAMS sample was dried at room temperature, whereas VAMS samples under humidity controlled conditions showed more than 85% of recovery. Our results suggest that adequate level of humidity control was critical to ensure sample stability of ASA, and this humidity control could also be achieved at home using household vacuum sealer, thus enabling patient-centric clinical trials to be conducted.