Dual immunostaining of cervical cytology specimens with atypical squamous cells for p16/Ki-67 does not exclude the existence of a high-grade squamous intraepithelial lesion

This study was conducted to evaluate the accuracy of p16/Ki-67 dual immunostaining compared to high-risk human papillomavirus (HR-HPV) DNA testing for cervical intraepithelial neoplasia (CIN) in women with atypical squamous cells, cytology not excluding high-grade squamous intraepithelial lesion (ASC-H). Data were collected from 73 patients diagnosed to have ASC-H on a Pap smear who were HPV genotyped and had histological examination of a cervical biopsy. The CINtec®PLUS kit was used on residual liquid-based material, and the immunoreactivity of dual-stained cells was graded according to the number as follows: G1 (1–5 positive cells), G2 (6–10), G3 (11–20), and G4 (> 20). Accuracy was evaluated based on the histological examination of colposcopy-guided biopsy or cervical conization on follow-up. Of the 70 patients with available data, positive p16/Ki-67 was associated with histological severity as follows: 15 % in negative histology, 67 % in CIN 1, 90 % in CIN 2, and 100 % in CIN 3. The average grade of positive p16/Ki-67 staining also increased from 0.2 in histologically negative cases to 1.2 in CIN 1, 2.4 in CIN 2, and 2.9 in CIN 3 (p < 0.01). For patients with CIN 2 or higher, p16/Ki-67 had a sensitivity of 94.6 % and a specificity of 75.8 %, while HR-HPV testing showed a sensitivity of 67.6 % and a specificity of 66.7 %. p16/Ki-67 immunostaining demonstrated better accuracy than HR-HPV for detecting CIN 2 or higher in patients with ASC-H cytology. Given the higher concordance with histological diagnosis, the grading system of positive p16/Ki-67 can be a useful adjunct for predicting high-grade lesions in clinical practice.