Lyophilization of premixed COVID‐19 diagnostic RT‐qPCR reactions enables stable long‐term storage at elevated temperature

Hammerling, Michael J.; Warfel, Katherine F.; Jewett, Michael C.

Reverse transcriptase‐quantitative polymerase chain reaction (RT‐qPCR) diagnostic tests for SARS‐CoV‐2 are the cornerstone of the global testing infrastructure. However, these tests require cold‐chain shipping to distribute, and the labor of skilled technicians to assemble reactions and interpret the results. Strategies to reduce shipping and labor costs at the point‐of‐care could aid in diagnostic testing scale‐up and response to the COVID‐19 outbreak, as well as in future outbreaks. In this study we test both lab‐developed and commercial SARS‐CoV‐2 diagnostic RT‐qPCR mixes for the ability to be stabilized against elevated temperature by lyophilization. Fully assembled reactions were lyophilized and stored for up to a month at ambient or elevated temperature and were subsequently assayed for their ability to detect dilutions of synthetic SARS‐CoV‐2 RNA. Of the mixes tested, we show that one commercial mix can maintain activity and sensitivity after storage for at least 30 days at ambient temperature after lyophilization. We also demonstrate that lyoprotectants such as disaccharides can stabilize freeze‐dried diagnostic reactions against elevated temperatures (up to 50°C) for at least 30 days. We anticipate that the incorporation of these methods into SARS‐CoV‐2 diagnostic testing will improve testing pipelines by reducing labor at the testing facility and eliminating the need for cold‐chain shipping.