Is p16(INK4A) expression more useful than human papillomavirus test to determine the outcome of atypical squamous cells of undetermined significance-categorized Pap smear? A comparative analysis using abnormal cervical smears with follow-up biopsies.
OBJECTIVE
To correlate high-risk human papillomavirus (HR-HPV) viral load to p16(INK4A) expression in atypical squamous cells of undetermined significance (ASCUS)-categorized Pap smears with follow-up biopsies in order to elucidate their relationships in gynecological pathology.


METHODS
We studied 66 ASCUS-categorized Pap smears with subsequent follow-up biopsies. HR-HPV viral load was determined by Hybrid Capture II assay from the cervical swab in each ASCUS-diagnosed Pap smear. Both smears and biopsies were immunostained with a primary anti-p16 antibody, clone E6H4, and we analyzed the correlations between HR-HPV viral load in each ASCUS-diagnosed Pap smear and p16 expression of smears with follow-up biopsies.


RESULTS
Correlation analyses of the corresponding histological diagnoses from 66 ASCUS-diagnosed Pap smears revealed that 21 (32%) cases had only reactive changes and 45 cases showed cervical intraepithelial neoplasia including LSIL (24 cases, 36%) and HSIL or higher (21 cases, 32%). Tests for HR-HPV viral load revealed 17 (26%) negative cases and 49 (74%) positive cases. Immunostaining showed that 26 cases (39%) were negative and 40 (61%) were positive for p16 expression. Comparative analysis of these two tests indicated consistencies as well as discrepancies. They showed significant differences (P < 0.001) between negative p16 expressions of Pap smears with the presence of reactive lesions in follow-up biopsies and HR-HPV viral load. However, no significant difference (P = 0.739 and 0.606) between p16 expression of Pap smears with the presence of LSIL, HSIL or higher in follow-up biopsies and high HR-HPV viral load was found. In addition, there were significant differences (P < 0.001) in specificity and positive predictive value, but no significant differences were found in sensitivity (P = 0.606) and negative predictive value (P = 0.062) between p16 immunostaining and HR-HPV viral load.


CONCLUSIONS
The results indicate that there is a close association between weak or strong p16 expressions in ASCUS-categorized smears with the presence of SILs in follow-up biopsies and positive HR-HPV viral loads. Conversely, there is also a clear association between the lack of p16 expression and the absence of significant lesions in follow-up biopsies, but this is not consistent with a negative HR-HPV viral load. It is concluded that p16 expression is an indicator of pathogenic activity of HR-HPV, which is an objective biomarker for clarification of ASCUS-categorized Pap smears in gynecological cytopathology. Furthermore, through comparative analysis, directly visualized p16 immunostaining on smears appears to be a more effective method than HR-HPV viral load for the detection of reactive changes and LSILs from ASCUS-categorized Pap smears.
Nieh
Shin
S
Department of Pathology, School of Medicine, National Defense Medical Center and Tri-Service General Hospital, No. 325, Cheng-Kung Road, Sec. 2, Neihu 114, Taipei, Taiwan, Republic of China. niehshin1014@yahoo.com.tw
Chen
Su-Feng
SF
Chu
Tang-Yuan
TY
Lai
Hung-Cheng
HC
Lin
Yaoh-Shiang
YS
Fu
Earl
E
Gau
Ching-Hwa
CH
D014408:Biomarkers, Tumor / Q000096:biosynthesis; D001706:Biopsy; D002584:Cervix Uteri / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis*; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology / Q000821:virology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D027383:Papillomaviridae; D030361:Papillomavirus Infections / Q000378:metabolism* / Q000821:virology; D014412:Tumor Virus Infections / Q000378:metabolism* / Q000821:virology; D002583:Uterine Cervical Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D019562:Viral Load; D002578:Uterine Cervical Dysplasia / Q000378:metabolism* / Q000473:pathology / Q000821:virology
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16