Triage of LSIL/ASC-US with p16/Ki-67 dual staining and human papillomavirus testing: a 2-year prospective study

OBJECTIVE: To investigate human papillomavirus (HPV) DNA testing and p16/Ki-67 staining for detecting cervical intraepithelial grade 2 or worse (CIN2+) and CIN3 in women referred to colposcopy with minor abnormal cervical cytology low-grade squamous intraepithelial lesions (LSIL) and atypical squamous cells of undermined significance (ASC-US). The clinical performance of both tests was evaluated as stand-alone tests and combined, for detection CIN2+ and CIN3 over 2 years. METHODS: ThinPrep(®) liquid-based cytology (LBC) specimens were collected from 1349 women with repeat LSIL or ASC-US. HPV DNA was performed using Hybrid Capture. Where adequate material remained (n = 471), p16/Ki-67 overexpression was assessed. Clinical performance for detection of histologically diagnosed CIN2+ and CIN3 was calculated. RESULTS: Approximately 62.2% of the population were positive for HPV DNA, and 30.4% were positive for p16/Ki-67. p16/Ki-67 showed no significant difference in positivity between LSIL and ASC-US referrals (34.3% versus 28.6%; P = 0.189). Women under 30 years had a higher rate of p16/Ki-67 compared to those over 30 years (36.0% versus 26.6%; P = 0.029). Overall HPV DNA testing produced a high sensitivity for detection of CIN3 of 95.8% compared to 79.2% for p16/Ki-67. In contrast, p16/Ki-67 expression offered a higher specificity, 75.2% versus 40.4% for detection of CIN3. Combining p16/Ki-67 with HPV DNA improved the accuracy in distinguishing between CIN3 and <CIN3. The absolute risk of CIN3 increased from 15.6% in women who were HPV DNA positive to 27% in women positive for HPV DNA and p16/Ki-67. Those negative for HPV DNA and p16/Ki-67 had a low risk of 1.2% of CIN3. CONCLUSION: The addition of p16/Ki-67 to HPV DNA testing leads to a more accurate stratification of CIN in women presenting with minor cytological abnormalities.