We examined DNA from cervical swabs of 7 women with a cervical intraepithelial neoplasia grade 2 or worse (CIN2+) who were negative by HPV DNA testing. For control purposes, 106 cytology negative/HPV-negative samples were included. PCR was performed with either 1 μL of DNA solution or different amounts of input DNA (25, 50, and 100 ng). We tested two different commercial alkaline phosphatases (ALPs) at two distinct reaction times. The overall conclusions were based on HPV Blot, type-specific PCR, direct sequencing, and real-time quantitative PCR (qPCR).
All seven patients with CIN2+ disease turned HPV-positive when 100 ng of input DNA and E6 type-specific PCR were used. Discrepant and false-negative results were obtained using different amounts of input DNA. Different commercial ALPs showed a significant impact on detection performance. Analysis of viral load indicated that the detection threshold for HPV infection using SPF1/GP6+ PCR plus HPV Blot was approximately 102–103 copies.
Reliable determination of HPV status is crucially dependent on the amount of input genomic DNA.