Evaluation of CINtec PLUS® testing as an adjunctive test in ASC-US diagnosed SurePath® preparations

The CINtec PLUS® system is an immunohistochemical cocktail composed of antibodies against p16(INK4a) (surrogate of HPV infection) and Ki-67 (proliferation marker) meant to improve the sensitivity and specificity for detecting high-grade dysplasia (HGD). In the presence of dysplasia, a red chromogen marks Ki-67 expression in the nucleus and a brown chromogen marks cytoplasmic p16(INK4a) expression. Only cells showing dual staining are interpreted as positive. This retrospective study examined the performance of CINtec PLUS testing when performed on ASC-US diagnosed samples. Comparison was made to high-risk HPV DNA test results and colposcopic biopsy results. Technical considerations in the interpretation of this immunohistochemical stain are additionally discussed. CINtec PLUS showed modest sensitivity (64%) and specificity (53%) in identifying the presence of HGD at surgical biopsy. Positive and negative predictive values for HGD were 28% and 83%, respectively. HR-HPV DNA test yielded sensitivity of 100% and specificity of 21%. During interpretation, squamous metaplasia and endocervical cells were seen to show individual staining for p16(INK4a) or Ki-67. Individual staining, when present within three dimensional cellular groups common to SurePath® preparations, can be time-intensive to interpret necessitating thoughtful examination at high power. The Pap test with HR-HPV DNA testing is a highly sensitive test. A specific test is needed to prevent false positives and over treatment. The CINtec® system provides a modest increase in specificity beyond HR-HPV DNA testing. Future study of its appropriateness and cost-ffectiveness in a treatment algorithm are warranted.