Role of quantitative p16(INK4A) mRNA assay and digital reading of p16(INK4A) immunostained sections in diagnosis of cervical intraepithelial neoplasia.
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Int J Cancer
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Visual interpretation of cervical biopsies is subjective and variable, generally showing fair to moderate inter-reader agreement in distinguishing high from low grade cervical intraepithelial neoplasia (CIN). We investigated the performance of two objective p16 quantitative tests in comparison with visual assessment: (i) p16-mRNA assay and (ii) digital analysis of sections stained for p16 protein. The primary analysis considered 232 high-risk human papilloma virus positive (HPV+) samples from diagnostic cervical specimens. A p16 RT-qPCR (p16-mRNA assay) was run on mRNA extracted from formalin-fixed paraffin-embedded sections. Two p16 immunohistochemistry (IHC) readings, a visual read by a histopathologist (Visual IHC) and a digital read of a high-resolution scan (Digital IHC), were done on adjacent sections. The worst reviewed CIN grade (agreed by at least two histopathologists) from up to two biopsies and a loop excision was taken, with CIN2/3 as the primary endpoint. Visual IHC attained a specificity of 70% (95%CI 61-77) for 85% (95%CI 77-91%) sensitivity. The four-point Visual IHC staining area under the curve (AUC) was 0.77 (95%CI 0.71-0.82), compared with 0.71 (95%CI 0.64-0.77) for p16-mRNA and 0.67 (95%CI 0.60-0.74) for Digital IHC. Spearman rank-order correlations were: visual to p16-mRNA 0.41, visual to digital 0.49 and p16-mRNA to digital: 0.22. The addition of p16-mRNA assay to visual reading of p16 IHC improved the AUC from 0.77 to 0.84 (p = 0.0049). p16-mRNA testing may be complementary to visual IHC p16 staining for a more accurate diagnosis of CIN, or perhaps a substitute in locations with a lack of skilled pathologists.