Alternatives to Viral Transport Medium for Use in SARS-CoV-2 Sample Preparation
Technical Report,01 Apr 2020,17 Apr 2020
SCHOOL OF AEROSPACE MEDICINE WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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The COVID19 outbreak has severely impacted laboratory supply chains for all materials required for testing. This supply chain concern has begun to impact the reagents needed for sample collection and transport. In a news article released by National Public Radio, the apparent decrease in new tests seen by contract laboratories like Labcorp and Quest can partially be attributed to a limited supply of VTM. To address this gap in sample transport supplies before it becomes a critical point within the MHS, GEIS requested USAFSAMPHT perform a bridge study to evaluate the performance of saline and RNAlater as alternative transport media. We performed a six-point dilution series over three days and a freeze-thaw cycle to determine the performance the CDC SARS-CoV-2assay in samples near the limit of detection prepared in RNAlater or buffered saline. Our results indicate that samples prepared in buffered saline and frozen encounter no reduction in assay sensitivity or increase in variability, but even after only 24 hours of refrigeration the saline samples begin to degrade. In contrast, RNAlater successfully stabilized refrigerated samples with no change in performance over 72 hours of refrigeration, but freezing RNAlater-stabilized samples resulted in decreased assay performance for concentrations near the lower limit of detection. We recommend advising GEIS partner network and MHS clinical labs to collect NPOP swabs in RNAlater or buffered saline and for sample transport on dry ice to USAFSAM and updating EUA submissions with reference to this bridge study demonstrating suitability of RNAlater and saline as alternative sample collection and transport materials.
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