p16/Ki-67 Dual Stain Cytology for Detection of Cervical Precancer in HPV-Positive Women

Abstract

Background: Human papillomavirus (HPV)-based cervical cancer screening requires triage markers to decide who should be referred to colposcopy. p16/Ki-67 dual stain cytology has been proposed as a biomarker for cervical precancers. We evaluated the dual stain in a large population of HPV-positive women.

Methods: One thousand five hundred and nine HPV-positive women screened with HPV/cytology cotesting at Kaiser Permanente California were enrolled into a prospective observational study in 2012. Dual stain cytology was performed on residual Surepath material, and slides were evaluated for dual stain-positive cells. Disease endpoints were ascertained from the clinical database at KPNC. We evaluated the clinical performance of the assay among all HPV-positive women and among HPV-positive, cytology-negative women. We used internal benchmarks for clinical management to evaluate the clinical relevance of the dual stain assay. We evaluated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the dual stain compared with Pap cytology. All statistical tests were two-sided.

Results: The dual stain had lower positivity (45.9%) compared with cytology at an ASC-US threshold (53.4%). For detection of CIN2+, the dual stain had similar sensitivity (83.4% vs 76.6%, P = .1), and statistically higher specificity (58.9% vs 49.6%, P < .001), PPV (21.0% vs 16.6%, P < .001), and NPV (96.4% vs 94.2%, P = .01) compared with cytology. Similar patterns were observed for CIN3+. Women with a positive test had high enough risk for referral to colposcopy, while the risk for women with negative tests was below a one-year return threshold based on current US management guidelines.

Conclusion: Dual stain cytology showed good risk stratification for all HPV-positive women and for HPV-positive women with normal cytology. Additional follow-up is needed to determine how long dual stain negative women remain at low risk of precancer.

Figure 1.

CONSORT diagram of the study population. DS+ = dual stain–positive subjects; HC2 = Hybrid Capture 2; HPV = human papillomavirus.

Figure 2.

Risk of cervical precancer according to dual stain result in relation to clinical management thresholds. Risk of CIN2 or greater (A) and CIN3 or greater (B) in all HPV-positive women and in HPV-positive/cytology-negative women according to dual stain results. Point estimates of absolute risk (positive predictive value for DS-positive women, complement of the negative predictive value for DS-negative women) are shown as boxes with vertical lines indicating 95% confidence intervals. Percent estimates in parenthesis indicate the proportion of dual stain positive and dual stain negative women. The dashed line indicates the risk in women with HPV-positive ASC-US (threshold for referral to colposcopy), and the dotted line indicates the risk in HPV-positive/cytology-negative women (threshold for one-year return). DS+ = dual stain; HPV = human papillomavirus; NILM = negative for intraepithelial lesion or malignancy.