A new solid matrix for preservation of viral nucleic acid from clinical specimens at ambient temperature

Stabilizing paper matrix methods for retaining nucleic acid from inactivated clinical specimens offer a solution for molecular diagnostics when specimens may be stored or shipped at ambient temperature. We developed cellulose disks (UNEXP) saturated with a total nucleic acid extraction buffer (UNEX) modified from a previously developed lysis buffer for multiple enteric pathogens. Infectivity of hepatitis A virus, adenovirus and poliovirus was destroyed after 2-3 h incubation at room temperature on the UNEXP disks. Norovirus RNA could be detected in UNEXP-eluted nucleic acids by reverse transcription-quantitative PCR (RT-qPCR) from 54 stool samples after 2 weeks storage at room temperature on disks; a subset of seven samples were positive after 3 months storage. Genotyping was successful in 76% of 54 samples tested including six of seven samples stored on the UNEXP disks for up to one month. Comparison of UNEXP with the FTA elute card in a subset of 10 samples demonstrated similar detection and genotyping rates after two weeks of storage at room temperature. UNEXP disks could be useful for epidemiologic investigations of disease outbreaks in resource-limited areas by simplifying specimen transport to regional diagnostic laboratories or shipment to international centers without the need to ship samples on dry ice.