Polymerase chain reaction (PCR) and indirect in situ hybridization were combined to detect human papillomavirus (HPV) DNA on Papanicolaou (PAP)-stained cervical smears. To our knowledge, this is the first report of an experiment using indirect in situ PCR (IS-PCR) on PAP-stained cervical smears.
We collected native cell specimens from cervicovaginal lavage of 162 patients with squamous intraepithelial lesions. Solution-phase PCR (SP-PCR) was performed as the reference method in the detection of HPV DNA. Indirect IS-PCR was carried out for the same patients to detect the HPV DNA types 6/11 and 16/18 after the PAP-stained smears had been decolorized. Low-risk and high-risk HPV DNA types were also detected by both SP-PCR and indirect IS-PCR.
In the evaluation by indirect IS-PCR, 48 of 81 PAP-stained cell smears of low-grade squamous intraepithelial lesions were positive for HPV DNA, as compared to 40 positive cell smears determined by indirect SP-PCR (sensitivity of indirect IS-PCR compared to SP-PCR, 98.1%). Forty-two of 42 high-grade squamous intraepithelial lesion samples were positive for HPV DNA, as determined by both methods (sensitivity of IS-PCR, 100%). Cell lines investigated in this study as positive or negative controls for HPV DNA were confirmed by indirect IS-PCR and SP-PCR.
Our data show that in comparison to SP-PCR, indirect IS-PCR is a highly sensitive method to detect HPV DNA in cell smears from the uterine cervix. The advantages of indirect IS-PCR are (a) low numbers of cells needed, (b) the possibility of using PAP-stained specimens, and (c) cytologic details of smears can be preserved.