MIB-1 and PCNA immunostaining as a diagnostic adjunct to cervical Pap smear

The present study was done to determine the role of MIB-1 (Molecular Immunology Borstel) and proliferating cell nuclear antigen (PCNA) proliferative index as a diagnostic adjunct to cervical Papanicolaou (Pap) smear for the identification of ascending grades of cervical intraepithelial neoplasia (CIN) developing into cancer in the human uterine cervix. A total of 49 adequate Pap smears with consensus diagnosis were destained for immunocytochemical staining (MIB-1 and PC10). Staining was done by streptavidin-biotin method after antigen retrieval. MIB-1 and PC10 labeling index (LI) were calculated in each case and divided into three groups, i.e., <10%, 10-20%, and >20%, respectively. Statistical analysis was done by using the SPSS 10.0 package. The comparisons were made using analysis of variance (ANOVA) and independent sample t-test. Bivariate and Pearson's correlation coefficient were used to obtain correlations between different groups. Out of 49 cases, 40 cases (81.6%) showed positive immunostaining with MIB-1 and PCNA. Proliferative LI of MIB-1 and PCNA increased with the ascending grades of CIN lesions to carcinoma. The highest proliferative index (mean +/- SD) for PCNA and MIB-1 were observed for the carcinoma group (PCNA LI, 39.200 +/- 1.6865; MIB-1LI, 35.300 +/- 1.8886). A significant positive correlation between ascending grades of squamous intraepithelial lesion (SIL) and labeling indices of markers (r = 0.87 for MIB-1 and r = 0.88 for PCNA) suggests that MIB-1/PCNA proliferative markers can be used as an adjunct to cytomorphological interpretation of conventional cervical Pap smear.