Determination of detection efficiency and limit of rtPCR system using Lentivirus. (A) A standard calibration curve of Ct vs. genomic copy number was generated based on rtPCR results from LTR targeting primer set and known genomic copy number of LTR. (B) rtPCR results for RNA extraction by QIAmp kit or Trizol-based method. The known number of Lentivirus was tested with the two extraction methods and compared. (C) The average Ct values are compared between QIAmp and Trizol methods.