Determinants of p16/Ki-67 adequacy and positivity in HPV-positive women from a screening population.

BACKGROUND: The objective of this study was to describe the determinants of adequacy and positivity of the p16/Ki-67 assay in a human papillomavirus (HPV)-positive screening population enrolled within the New Technologies for Cervical Cancer 2 (NTCC2) study. METHODS: ThinPrep slides were immunostained for p16/Ki-67; each slide had 3 reports from different laboratories. The authors included population-related, sampling-related/staining-related, and interpretation-related variables in the analyses. Adequacy and positivity proportions were stratified by variables of interest. Univariate and multivariate logistic models were used to identify determinants of adequacy and positivity. RESULTS: In total, 3100 consecutive HPV-positive cases were analyzed. Because every slide was interpreted by 3 centers, 9300 reports were obtained, including 905 (9.7%) that were inadequate and 2632 (28.3%) that were positive. The percentage of cases in which all 3 reports were inadequate increased with increasing age of the women and with inadequate cytology. The highest percentage of adequacy in all 3 reports and of cases with all 3 reports positive was observed in specimens from women who had grade ≥2 cervical intraepithelial neoplasia (CIN2+), atypical squamous cells of undetermined significance or more severe (ASC-US+) cytology, or mRNA positivity. The number of inadequate reports was significantly associated with increasing age, inadequate cytology, mRNA negativity, and scant cellularity. A positive p16/Ki-67 report was associated with an ASC-US+ result and with a positive mRNA result in cases both with and without CIN2+ but was associated with an HPV type 16 and/or 18 infection only in CIN2+ cases. The presence of CIN2+ was strongly associated with dual staining positivity. CONCLUSIONS: The interpretation of p16/Ki-67 results may be influenced by several different variables, all of which are part of the steps in the procedure, and by the characteristics of the screened population.

Interlaboratory concordance of p16/Ki-67 dual-staining interpretation in HPV-positive women in a screening population.

BACKGROUND: p16/Ki-67 dual staining is a candidate biomarker for triaging human papillomavirus (HPV)-positive women. Reproducibility is needed for adopting a test for screening. This study assessed interlaboratory reproducibility in HPV-positive women. METHODS: All women positive for HPV from the Italian New Technologies for Cervical Cancer 2 study, were included in this study. ThinPrep slides were immunostained for p16/Ki-67 in 4 laboratories and were interpreted in 7 laboratories. Each slide had 3 reports from different laboratories. Slides were classified as valuable or inadequate, and valuable slides were classified as positive (at least 1 double-stained cell) or negative. Interlaboratory reproducibility was evaluated with κ values. RESULTS: Overall, we obtained 9300 reports for 3100 cases; 905 reports (9.7%) were inadequate. The overall adequacy concordance was poor (κ = 0.224; 95% confidence interval [CI], 0.183-0.263). The overall positivity concordance was moderate (κ = 0.583; 95% CI, 0.556-0.610). Of the 176 cervical intraepithelial neoplasia 2+ (CIN-2+) lesions found in HPV DNA-positive women, 158 had a valid result: 107 were positive in all 3 reports (sensitivity for CIN-2+, 67.7%; 95% CI, 59.8%-74.9%), 23 were positive in 2 reports (sensitivity of the majority report, 82.3%; 95% CI, 75.4%-87.9%), and 15 were positive in 1 report (sensitivity of at least 1 positive result, 91.8%; 95% CI, 86.3%-95.5%). Thirteen CIN-2+ cases were negative in all 3 reports. The overall positivity concordance in CIN-2+ samples was κ = 0.487 (95% CI, 0.429-0.534), whereas in the non-CIN-2+ samples, it was κ = 0.558 (95% CI, 0.528-0.588). CONCLUSIONS: The p16/Ki-67 assay showed poor reproducibility for adequacy and good reproducibility for positivity comparable to that of cervical cytology. Nevertheless, the low reproducibility does not affect the sensitivity for CIN-2+.

Interobserver reproducibility of cytologic p16INK4a /Ki-67 dual immunostaining in human papillomavirus-positive women.

BACKGROUND: The accumulation of cyclin-dependent kinase inhibitor 2A (p16ink4a ) protein in a cell is associated with neoplastic progression in precancerous cervical lesions. Dual staining for p16ink4a and Ki-67 has been proposed as a triage test in cervical cancer screening for women who test positive for human papillomavirus DNA. In this study, interobserver reproducibility of the interpretation of this test was assessed. METHODS: Forty-two immunostained, liquid-based cytology slides were divided into 2 sets and were interpreted by 17 to 21 readers from 9 different laboratories, yielding a total of 816 reports. Immunostaining results were classified as positive, negative, inconclusive, or inadequate. After evaluation of the first set of slides and before circulation of the second set, the results were discussed in a plenary meeting. The 10 slides with the most discordant results were evaluated again by selected expert cytopathologists. RESULTS: The overall κ value was 0.612 (95% confidence interval [CI], 0.523-0.701), it was higher for the positive and negative categories (κ = 0.692 and κ = 0.641, respectively), and it was almost null for the inconclusive category (κ = 0.058). Considering only readers from laboratories with documented experience, the κ value was higher (κ = 0.747; 95% CI, 0.643-0.839) compared with nonexperienced centers (κ = 0.498; 95% CI, 0.388-0.616). The results were similar in both sets of slides (κ = 0.505 [95% CI, 0.358-0.642] and κ = 0.521 [95% CI, 0.240-0.698] for the first and second sets, respectively). Reinterpretation of the slides with the most discordant results did not provide any improvement (first evaluation, κ = 0.616 [95% CI, 0.384-0.866]; second evaluation, κ = 0.403 [95% CI, 0.182-0.643]). CONCLUSIONS: Dual staining for p16 ink4a and Ki-67 demonstrated good reproducibility, confirming its robustness, which is a necessary prerequisite for its adoption as a triage test in cervical cancer screening programs that use human papillomavirus DNA as a primary test. Cancer Cytopathol 2017;125:212-220. © 2016 American Cancer Society.