Amplification of HPV RNA by PreTect HPV-Proofer. The PreTect HPV-Proofer assay detects HPV E6 and E7 mRNA from the high-risk HPV types 16, 18, 31, 33, and 45. The assay is based on real-time multiplex NASBA, detecting in complex HPV-16 and the sample performance control U1A (a), HPV-33 and HPV-45 (b), and HPV-31 and HPV-18 (c). A positive reaction result is revealed as a sigmoid curve.