The Predictive Value of p16INK4a and Hybrid Capture 2 Human
The Predictive Value of p16INK4a and Hybrid Capture 2 Human
We performed p16 immunocytochemical analysis and Hybrid Capture 2 (HC2, Digene, Gaithersburg, MD) high-risk HPV testing on 210 abnormal SurePath (TriPath Imaging, Burlington, NC) Papanicolaou specimens diagnosed as low-grade squamous intraepithelial lesion (LSIL) or high-grade squamous intraepithelial lesion (HSIL). The results were compared with 121 follow-up biopsy specimens. p16 was positive in 57.9% of women with LSIL compared with 97.1% of women with HSIL. In contrast, HC2 testing was positive in 85.0% of women with LSIL and 86.4% of women with HSIL. The differences in the positive rates for16 between LSIL and HSIL was significant (P < .001), whereas for HC2 it was not (P = .264). In patients who had cervical biopsies following a cytologic diagnosis of LSIL, the positive predictive value (PPV) of p16 for a biopsy of cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3; 33%) was significantly higher than the PPV of HC2 results (21%) (P < .001). Using liquid-based cytology specimens, p16 immunocytochemical analysis has a higher PPV than reflex HC2 HPV testing for identifying CIN2/3 among patients with LSIL and might be useful for selecting patients with LSIL for colposcopy.
In the United States, approximately 1 million patients are diagnosed as having a low-grade squamous intraepithelial lesion (LSIL), and more than 2 million Papanicolaou (Pap) results of atypical squamous cells of undetermined significance (ASC-US) are reported annually. The subsequent evaluation of women with this large number of mildly abnormal Pap results places a heavy burden on health care resources. The National Cancer Institute sponsored the ASC-US/LSIL Triage Study (ALTS) to compare 3 management strategies for women with ASC-US or LSIL. These consisted of immediate colposcopy, repeated Pap testing, and reflex Hybrid Capture 2 (HC2, Digene, Gaithersburg, MD) human papillomavirus (HPV) testing. For ASC-US, the study demonstrated that HC2 HPV testing had a higher sensitivity for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3; 95.9%-96.3%) than a single repeated ThinPrep Pap test (Cytyc, Boxborough, MA) (85.0%-85.3%). Based on the study, the American Society of Colposcopy and Cervical Pathology (ASCCP) recommended that women with a diagnosis of ASC-US should be managed using a program of 2 repeated Pap tests, immediate colposcopy, or HC2 DNA testing for high-risk HPV. If liquid-based cytology was used, reflex HC2 HPV testing was considered the preferred strategy.
A cytologic diagnosis of LSIL is associated with changes in the cervical epithelium that range from slight viral cytopathic effects to dysplasia bordering on and often including CIN2/3. The ALTS study found that 83.6% of women with LSIL were positive for high-risk HPV, and the ASCCP recommended that women older than 18 years with a cytologic diagnosis of LSIL be referred for colposcopy. To avoid an excessive amount of intervention for low-grade lesions, reflex HC2 testing for LSIL was recommended for postmenopausal women and the women younger than 18 years as an alternative to immediate colposcopy.
HPV DNA testing is based on the etiologic relationship of high-risk types of HPV with cervical cancer. High-risk HPV DNA can be detected in almost all high-grade CIN and cervical cancers. From a screening study of 7,932 women, Clavel et al reported that 23% of women 21 to 30 years old had high-risk HPV infections. For the majority of women, HPV infections are transient and last approximately 8 to 10 months. It is the persistent infections that integrate viral DNA into cells that are likely to induce CIN2/3. Although repeated positive high-risk HPV testing results strongly predict a risk of developing CIN2/3, a single positive result might not indicate the presence of high-grade CIN.
The presence of high-risk HPV in nearly all high-grade CIN confers a high sensitivity on HC2 testing for the detection of CIN2/3. Clavel et al reported a sensitivity of 100% for HC2 among 7,932 women having cervical biopsies showing CIN2/3. In the ALTS study of 3,488 women having ASC-US Pap smear results, HC2 testing had a sensitivity of 95.9% for the detection of CIN2 and 96.3% for CIN3. Because of the high prevalence of high-risk HPV infection and the low prevalence of CIN2/3, especially in young women, HPV testing alone has a limited ability to distinguish women with high-grade CIN from those with less severe cervical abnormalities. Clavel et al found that high-risk HPV testing had a positive predictive value (PPV) of 9.3% to 14.2% for the detection of CIN2/3, and in the ALTS study, PPVs for HC2 of 19.6% and 10.0% were observed for CIN2 and CIN3, respectively. Clearly, a test with a higher PPV and a lower false-positive fraction would improve the efficiency of cervical screening programs.
The overexpression of p16, a cyclin-dependent kinase inhibitor, is closely associated with high-risk HPV infection and high-grade CIN. Hu et al recently reported that in cervical biopsy specimens, the staining pattern of p16 and the proportion of positive cells are closely related to high-risk HPV types 16 and 18 infection and with CIN2/3. These results and the studies of p16 on liquid-based cytology specimens by Bibbo et al and Saqi et al suggest that p16 can be used in cervical screening as a marker for persisting high-risk HPV infection and high-grade squamous intraepithelial lesion (HSIL)and can be useful in resolving ambiguous cases involving a differential diagnosis of cervical neoplasia. The present study was undertaken to investigate the relative efficacy of p16 immunocytochemical analysis and HC2 testing to predict a cytologic diagnosis of HSIL and a biopsy diagnosis of CIN2/3 using SurePath (TriPath Imaging, Burlington, NC) cytology specimens.
We performed p16 immunocytochemical analysis and Hybrid Capture 2 (HC2, Digene, Gaithersburg, MD) high-risk HPV testing on 210 abnormal SurePath (TriPath Imaging, Burlington, NC) Papanicolaou specimens diagnosed as low-grade squamous intraepithelial lesion (LSIL) or high-grade squamous intraepithelial lesion (HSIL). The results were compared with 121 follow-up biopsy specimens. p16 was positive in 57.9% of women with LSIL compared with 97.1% of women with HSIL. In contrast, HC2 testing was positive in 85.0% of women with LSIL and 86.4% of women with HSIL. The differences in the positive rates for16 between LSIL and HSIL was significant (P < .001), whereas for HC2 it was not (P = .264). In patients who had cervical biopsies following a cytologic diagnosis of LSIL, the positive predictive value (PPV) of p16 for a biopsy of cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3; 33%) was significantly higher than the PPV of HC2 results (21%) (P < .001). Using liquid-based cytology specimens, p16 immunocytochemical analysis has a higher PPV than reflex HC2 HPV testing for identifying CIN2/3 among patients with LSIL and might be useful for selecting patients with LSIL for colposcopy.
In the United States, approximately 1 million patients are diagnosed as having a low-grade squamous intraepithelial lesion (LSIL), and more than 2 million Papanicolaou (Pap) results of atypical squamous cells of undetermined significance (ASC-US) are reported annually. The subsequent evaluation of women with this large number of mildly abnormal Pap results places a heavy burden on health care resources. The National Cancer Institute sponsored the ASC-US/LSIL Triage Study (ALTS) to compare 3 management strategies for women with ASC-US or LSIL. These consisted of immediate colposcopy, repeated Pap testing, and reflex Hybrid Capture 2 (HC2, Digene, Gaithersburg, MD) human papillomavirus (HPV) testing. For ASC-US, the study demonstrated that HC2 HPV testing had a higher sensitivity for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3; 95.9%-96.3%) than a single repeated ThinPrep Pap test (Cytyc, Boxborough, MA) (85.0%-85.3%). Based on the study, the American Society of Colposcopy and Cervical Pathology (ASCCP) recommended that women with a diagnosis of ASC-US should be managed using a program of 2 repeated Pap tests, immediate colposcopy, or HC2 DNA testing for high-risk HPV. If liquid-based cytology was used, reflex HC2 HPV testing was considered the preferred strategy.
A cytologic diagnosis of LSIL is associated with changes in the cervical epithelium that range from slight viral cytopathic effects to dysplasia bordering on and often including CIN2/3. The ALTS study found that 83.6% of women with LSIL were positive for high-risk HPV, and the ASCCP recommended that women older than 18 years with a cytologic diagnosis of LSIL be referred for colposcopy. To avoid an excessive amount of intervention for low-grade lesions, reflex HC2 testing for LSIL was recommended for postmenopausal women and the women younger than 18 years as an alternative to immediate colposcopy.
HPV DNA testing is based on the etiologic relationship of high-risk types of HPV with cervical cancer. High-risk HPV DNA can be detected in almost all high-grade CIN and cervical cancers. From a screening study of 7,932 women, Clavel et al reported that 23% of women 21 to 30 years old had high-risk HPV infections. For the majority of women, HPV infections are transient and last approximately 8 to 10 months. It is the persistent infections that integrate viral DNA into cells that are likely to induce CIN2/3. Although repeated positive high-risk HPV testing results strongly predict a risk of developing CIN2/3, a single positive result might not indicate the presence of high-grade CIN.
The presence of high-risk HPV in nearly all high-grade CIN confers a high sensitivity on HC2 testing for the detection of CIN2/3. Clavel et al reported a sensitivity of 100% for HC2 among 7,932 women having cervical biopsies showing CIN2/3. In the ALTS study of 3,488 women having ASC-US Pap smear results, HC2 testing had a sensitivity of 95.9% for the detection of CIN2 and 96.3% for CIN3. Because of the high prevalence of high-risk HPV infection and the low prevalence of CIN2/3, especially in young women, HPV testing alone has a limited ability to distinguish women with high-grade CIN from those with less severe cervical abnormalities. Clavel et al found that high-risk HPV testing had a positive predictive value (PPV) of 9.3% to 14.2% for the detection of CIN2/3, and in the ALTS study, PPVs for HC2 of 19.6% and 10.0% were observed for CIN2 and CIN3, respectively. Clearly, a test with a higher PPV and a lower false-positive fraction would improve the efficiency of cervical screening programs.
The overexpression of p16, a cyclin-dependent kinase inhibitor, is closely associated with high-risk HPV infection and high-grade CIN. Hu et al recently reported that in cervical biopsy specimens, the staining pattern of p16 and the proportion of positive cells are closely related to high-risk HPV types 16 and 18 infection and with CIN2/3. These results and the studies of p16 on liquid-based cytology specimens by Bibbo et al and Saqi et al suggest that p16 can be used in cervical screening as a marker for persisting high-risk HPV infection and high-grade squamous intraepithelial lesion (HSIL)and can be useful in resolving ambiguous cases involving a differential diagnosis of cervical neoplasia. The present study was undertaken to investigate the relative efficacy of p16 immunocytochemical analysis and HC2 testing to predict a cytologic diagnosis of HSIL and a biopsy diagnosis of CIN2/3 using SurePath (TriPath Imaging, Burlington, NC) cytology specimens.