Utility of Double Immunostaining for P16ink4a and MIB 1 (Ki-67) in Identification of HSIL Cells in Women with Preliminary ASCUS Pap Test Results.
Mamatha Chivukula, Nancy Mauser, Jonee Matsko, Teresa Friedman, Rudiger Ridder, Alexander Duwe, Marshall R Austin. Magee Women's Hospital of UPMC, Pittsburgh, PA; MTM Laboratories, Heidelberg, Germany
Background: ASCUS)/LSIL Triage Study have established adjunctive high risk HPV testing provides cost-effective basis for triage to colposcopy for women with ASCUS Paps who test HPV positive (+) versus return to routine screening for those who test HPV negative. HPV (+) ASCUS cases still have very limited positive predictive value for identifying women with underlying high grade CIN2/3. P16 is strongly over-expressed in nearly all high-grade pre-cancerous and malignant cervical lesions, detection of P16 over-expression has been proposed as a surrogate marker for the transforming activity of high-risk HPV. In order to assess the hypothesis that detection of individual cells simultaneously co-expressing P16 protein and proliferation marker Ki-67 can be used as an indicator for presence of CIN2/3, ina large prospective study on cervical cytology specimens, the aim of our study was to identify HSIL cells in women with preliminary ASCUS Pap test results.
Design: Residual fluid from liquid-based ThinPrep™ cytology specimens of women attending cervical cancer screening at a major tertiary hospital over a one year period were used for the analysis. Specimens with any abnormal Pap cytology result (ASC-US+) were included. For each case, an additional LBC slide was prepared and immuno-stained using a prototypic dual staining reagent kit (CINtec®Cytology, Dual stain) for the simultaneous detection of P16 and Ki-67 expression on the same slide. The presence of one or more individual cells co-expressing both P16 and Ki-67 were interpreted as “positive” test result. Follow-up biopsy and HPV results were obtained.
Results: A total of 1396 ASCUS Pap tests were assessed during the study, for which histopathologic follow-up has been available to date in 541 cases. Dual stain cells were identified in 15% of ASCUS Pap tests. Sensitivity of the Dual stain was 87.0% for CIN2+ and 95.7% for CIN3+, with specificity of 89.8% for non high-grade CIN. In ASC-US cases with positive HPV results, a positive Dual stain result identified all CIN3+ cases at high levels of specificity (up to 80%).
Conclusions: 1. Initial results from our cytology specimens subjected to simultaneous p16/Ki-67 dual staining and with biopsy follow-up indicate both high sensitivity and specificity for this novel screening approach to detection of histopathologic CIN2/3+. 2. Results showing high specificity rates for the dual stain support this approach as a promising adjunctive immunocytochemical test for detection of underlying histopathologic CIN2/3+.
Tuesday, March 1, 2011 9:30 AM
Poster Session III # 93, Tuesday Morning