Sensitivity of HPV tests on stained vs. unstained cervical smears

Objective To examine the effect of Papanicolaou staining of cervical,smears on the sensitivity of molecular biologic HPV tests. Study Design Two sensitive HPV tests were used, HPV DNA sequence analysis after polymerase chain reaction (PCR) amplification and the Hybrid Capture II method (HC II) (Digene Diagnostics Inc., Silver Spring, Maryland, U.S.A.). Papanicolaou-stained and unstained smears taken simultaneously were examined from 265 women readmitted for examination due to an atypical squamous cells of undetermined significance diagnosis. Results After an HPV test with the PCR method on unstained slides, 66% of the women were HPV positive, whereas the same women were HPV positive in 54% when Papanicolaou-stained slides were analyzed. However, this difference was not statistically significant (p > 0.1). With the HC II method, 55% of unstained smears were HPV positive whereas 29% were HPV positive, when Papanicolaoustained slides were examined. This difference was significant (p < 0.001). The same strong differences in sensitivity were observed when both the PCR and HC II, methods were studied on the same Papanicolaou stained glass slides, whereas on unstained slides no significant difference was found. Conclusion The results demonstrate that Papanicolaou staining of a cervical smear significantly decreases the sensitivity of an HPV test performed with the HC II method, whereas the PCR method is less affected. With the Papanicolaou method, the hematoxylin bath is followed by HCl treatment, and strong acid treatment destroys DNA.