Parallel Screening with Papanicolaou Smear and Visual Inspection Tests Significantly Reduced False Negative Screening Results in Southern Brazil

Abstract

Aims: To verify the screening performance of Pap smear and four modalities of visual inspection tests (VIT) in screening for cervical intraepithelial neoplasia CIN of grade 2, 3 or carcinoma in situ, in a low risk population. Study Design: A transversal study validated above tests, both in separate and in combination, against colposcopic and histologic examination as gold standard. Place and Duration of Study: RFCC (Portuguese abbreviation for “Female network against cancer”) in Florianópolis, southern Brazil, between June 2010 and July 2012. Methodology: Among 919 women eligible for the study, 882 completed all clinical and laboratory exams. All screen-positive and a random sample of 18.5% screen-negative specimen were submitted to colposcopy and, if necessary, histologic examination. Results: The prevalence of CIN2 + in this study was 1.7%. Pap smear as the only screening test produced about 1/3 of false negative results. Among those considered normal by Pap smear, 32.1% were diagnosed as CIN1 and 17.1% as CIN2 + by histological examination. The false negative rate reduction from 6/15 for Pap smear test alone to 1/15 for its combination with VIT as a parallel test represents a 5/15 or 33.3% reduction (95% CI = 12-62%). The combination of all four VIT modalities into a parallel test also reduced the false negative fraction significantly. Conclusions: This study has shown that Pap smear alone has its sensitivity too limited to be used as the only test in screening for cervical cancer. Adding VIT as a parallel test significantly improves the screening sensitivity by reducing the false negative results to less than 7% while maintaining the false negative rate at 8%.