Implementation of p16/Ki67 dual stain cytology in a Danish routine screening laboratory: Importance of adequate training and experience

Abstract

Background: Immunocytochemical staining with p16/Ki67 has been suggested as a promising triage biomarker in cervical cancer screening. As dual staining is a subjective method, proper training may be required to ensure safe implementation in routine laboratories and reduce risk of misclassification. We determined concordance between novice evaluators and an expert, stratified by number of slides reviewed at three reading points.

Methods: The study was conducted at the Department of Pathology, Randers, Denmark. Women were eligible if they were aged ≥45, had been enrolled in one of two ongoing clinical studies, and had a dual stain slide available. Dual staining was performed using the CINtec plus assay. Slides were randomly selected from three reading points at which novice evaluators had reviewed <30, ~300, and ≥500 dual stain slides respectively. Level of concordance was estimated using Cohen's Kappa, κ.

Results: Of 600 eligible slides, 50 slides were selected for review as recommended by the manufacturer. Median age was 68 years (range: 58-74). Overall concordance was good (κ = 0.68, 95% confidence interval [CI]: 0.60-0.76), with an overall agreement of 84% (95% CI: 70.9%-92.8%). Concordance improved with increasing number of slides reviewed at a given reading point, from a moderate concordance (κ = 0.47, 95% CI: 0.05-0.90) after reviewing <30 slides to a good concordance (κ = 0.66, 95% CI: 0.20-0.88) and a very good concordance (κ = 0.88, 95% CI: 0.66-1.00) after reviewing ~300 and ≥500 slides, respectively.

Conclusions: When interpreting dual stain slides from older women, concordance increased slightly as novice evaluators received more training and experience. Although further evaluation is warranted, these findings indicate that a significant amount of training and experience of novice evaluators may be needed to ensure accurate dual stain interpretation in this age group. Future studies should accurately describe training and experience of evaluators to enable a better comparison of concordance and diagnostic accuracy across studies.

Trial registration: NCT04114968 and NCT04298957.

Keywords: cervical cancer screening; cytology; dual stain; implementation; mass screening; training.

Conflict of interest statement

Roche Denmark has provided Cobas HPV‐DNA test kits and CINtec Plus test kits for the study at no cost. According to the contract between Roche and the Department of Public Health Programmes, Randers Regional Hospital, Denmark, the manuscript has been sent to Roche for review, but Roche had no influence on the scientific process and no editorial rights pertaining to this manuscript. The authors retained the right to submit the manuscript. AH and LWG have received a speaker's fee from Astra Zeneca, Denmark, outside of the submitted work. MT has received speaker's fees from Astra Zeneca, Denmark, and Roche Diagnostics, Denmark, outside of the submitted work. MT and BA have participated in other studies with HPV test kits sponsored by Roche and HPV self sampling devices sponsored by Axlab. The remaining authors declare no conflicts of interest.

© 2020 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Figures

FIGURE 1

The image illustrates one dual‐stain positive cell. Objective: X20

FIGURE 2

Staining characteristics of discordant cases. Arrows point to single dual‐stain positive cells. A strong background staining makes it difficult to determine whether the slide should be scored positive or not. Objective: X20