The main objective of this prospective observational study was to investigate the diagnostic performance of the p16/Ki-67 DST for detecting CIN 2+ in comparison with HR-HPV testing and Pap cytology in a LLETZ referral population. Secondary study objectives were investigation of the diagnostic performance of the DST for triage of patients with persistent low-grade CIN (ASCUS or LSIL cytology results during > 24 months) or an inconclusive colposcopy examination.
A total of 110 patients referred for a LLETZ were enrolled between October 2016 and mid-March 2017. From each participant, a cervical cytology sample was obtained before the onset of the LLETZ procedure. On each sample, we conducted the DST (Roche CINtec Plus Test ®), Pap cytology and an HPV DNA assay (identifying 17 different HPV types, including the 13 “high-risk” genotypes). Test results were correlated with the cone biopsy result to guarantee excellent disease ascertainment.
The overall disease prevalence of CIN 2+ was 56%. The mean age was 41 years, with 38% of patients being younger than 35 years. P16/Ki-67 positivity increased with histological severity. Positivity was 35% in CIN 0, 46.6% in CIN 1 and 80% in CIN 2 patients. Positivity increased to 95.9% and 100% in cases of a histological diagnosis of CIN 3 or invasive carcinoma. The overall sensitivity and specificity of the DST for detecting CIN 2+ was 94% and 58% respectively with a PPV of 74% and a NPV of 88%. HR-HPV testing results in a similar sensitivity of 92% but considerable lower specificity of 21% compared to the DST. When ASCUS or worse is considered a positive test result, Pap cytology still has the lowest sensitivity of 89% compared to dual staining and HR-HPV testing. In cases of persistent low-grade CIN (n=19), the DST had a non-inferior sensitivity of 100% and superior specificity of 67% for detecting CIN 2+ compared to HR-HPV testing. In cases of an inconclusive colposcopy examination, the DST provides a sensitivity of 95% and negative predictive value of 94% for detecting or excluding relevant disease.
The p16/Ki-67 DST provides high sensitivity and improved specificity compared to HR-HPV testing and Pap cytology for predicting CIN 2+, making it an interesting tool for identifying relevant disease in patients referred for a LLETZ. Test performances were even better in patients referred with persistent low-grade CIN, but conclusions should be drawn with care because of the low number of patients in this subgroup (n=19). In cases of an inconclusive colposcopy examination, the DST seems to provide an excellent negative predictive value for excluding almost all relevant disease.