Schematic representation of the primer design strategy and required DNA amplification reactions. A. For the E1-L1/E6E7 ratio analysis, six pairs of primers, corresponding to the gene regions E1, E2, E4E5, L2, L1 and E6E7, were evenly arranged along the genome sequence of HPV. The products of each primer pair were 1–2 kb in length. Of these pairs, the E2 and E6E7 primer pairs were used for the E2/E6E7 ratio analysis. All of the 12 component primers and their complementary sequences were also used in the DIPS-PCR. (refer to Additional file 2: Figure S1). B. The numbers of DNA amplification reactions respectively required by each detection technique are displayed.