Clinical role of p16INK4a expression in liquid-based cervical cytology: correlation with HPV testing and histologic diagnosis.

p16INK4a is overexpressed in high-risk human papillomavirus (HR-HPV)-infected preneoplastic and neoplastic lesions of the uterine cervix. Our aim was to verify whether p16 is a diagnostic marker also in cervical liquid-based cytology. We performed p16 immunocytochemical analysis and the Hybrid Capture 2 (HC2) test (Digene, Gaithersburg, MD) for HR-HPV infection in 471 ThinPrep-processed (Cytyc, Boxborough, MA) cervicovaginal samples and correlated the results with histologic findings. A total of 32.3% of the specimens showed p16 immunoreactivity, whereas the HC2 test was positive in 41.2% of the cases (65.2% concordance rate). Correlating the cytologic, p16, and HPV results with histologic findings revealed HC2 as the most sensitive test for a diagnosis of cervical intraepithelial neoplasia 2 or worse, whereas cytologic examination was the most specific. The positive predictive value was significantly higher for cytologic examination than for p16 and HR-HPV testing. These data suggest that p16 evaluation in ThinPrep samples does not have better clinical effectiveness for identifying high-grade lesions than conventional morphologic examination and HPV testing.