A novel pretreatment of dried blood spot filter paper to improve the preservation of amino acids: a technology to increase access and care.

Amino acids are vital biomarkers necessary for many critical metabolic pathways and therefore many disorders result in perturbations in amino acid concentrations. Recurrent measurements of amino acids are often necessary for disease management, especially in the inborn errors of metabolism, however many barriers exist restricting patient access to monitoring, especially for those living in rural and low resource areas. Dried blood spots (DBS) do not require medical expertise to obtain, allowing for an expedient method for the collection of multiple time points useful for diagnosis, monitoring, and research. Amino acids in a DBS, however, are highly susceptible to heat and humidity which are often encountered during the multiple days of transport via mailing-in of the sample. Thus, we sought to improve the stability of amino acids in a DBS when exposed to harsh environmental conditions. We showed that pretreatment of the card with ethylenediaminetetraacetic acid (EDTA), or a combination of phosphoric acid then EDTA (Phosphoric Acid-EDTA), significantly increased the consistency of sample recovery and accuracy, compared to untreated DBS. Sample precision was also significantly improved. EDTA pretreatment significantly reduced the amount of change in analyte concentration at high temperature and humidity, and Phosphoric Acid-EDTA pretreatment showed similar improvements at high heat without high humidity. Lastly, we evaluated EDTA pretreatment in "out-of-the-laboratory" collected samples compared to plasma. We show a significant improvement in the recovery and stability of amino acids exposed to harsh environmental conditions, even for multiple days, and thus allow for greater precision and accuracy of DBS sample analysis.