RNA extraction by isopropanol precipitation.

(A) TaqPath amplification curves of a mixture of human cell RNA and in vitro-transcribed SARS-CoV-2 N gene RNA purified using the Qiagen RNeasy Mini kit, QIAamp Viral RNA Mini kit, or isopropanol precipitation. Isopropanol precipitation gives RNA recovery better than the RNeasy kit and comparable to the QIAamp Viral kit. (B-C) Cq values of RNA from positive (Pos) and negative (Neg) NP swab samples in UTM, purified using either the Qiagen RNeasy Mini kit (squares) or isopropanol precipitation (diamonds). Reactions were performed using TaqPath master mix with the CDC SARS-CoV-2 N1 and N2 probes (blue and red points) and the human RNAse P (RP) control probe (yellow points). For points in the gray rectangle, no amplification was observed and Cq values were "undetermined" (Undet).