Dried urine spot as a stable, green, and practical microsampling tool in clinical practice for quantification of neopterin and creatinine

Abstract

Dried urine spot (DUS) is demonstrated to be a useful microsampling technique for neopterin and creatinine analysis. The method was verified using samples from 12 healthy volunteers, 12 cancer patients, and 12 patients infected with the SARS-CoV-2 virus and provided results comparable to the routine reference method. DUS samples were prepared using a simple dilute-and-shoot approach with a buffer solution prior to analysis. The developed method requires only 10 μL samples, making it feasible for home sampling when combined with commercially available pre-cut DUS devices with volumetric microfluidics or capillary transfer tubes. The method is environmentally friendly as it minimizes reagent use, requires only 110 μL phosphate buffer and no organic solvents. DUS also requires 250 times less storage space than liquid urine. The technique also improves laboratory work safety by minimizing the use of harmful extraction solvents. Dried samples are non-biohazardous and stable for up to 5 days at 40 °C and for 4 months at room temperature. This allows cost-effective transport via standard mail. The study also evaluated practical considerations for clinical laboratories and home sampling. Volumetric urine sampling is simple using capillary transfer tubes or commercially available volumetric microfluidic devices. When integrated with telemedicine, this microsampling approach can reduce unnecessary hospital visits for patients and improve patient access to clinical testing.