Bimanual examination should be performed to exclude frank invasion, or an ovarian or uterine mass.
A speculum is inserted to expose the cervix which is then examined through the colposcope. A magnification of x5-x25 is possible.
The presence of CIN is evaluated by:
- direct illumination - which may diagnose inflammation, infection, leukoplakia, condyloma or invasion
- illumination with a green filter - this helps to accentuate vascular patterns typical of CIN:
- mosaic and punctate patterns suggest CIN
- atypical, bizarre vessels suggest CIN or microinvasion (MI)
- staining with 5% acetic acid - this coagulates the protein in the cytoplasm and nuclei of the cells, so preventing light from passing through areas of high nuclear density, which thus appears white. Acetowhite changes may suggest:
- HPV, CIN, glandular intraepithelial neoplasia, or MI
- Schiller's test - normal mature squamous epithelium of vagina and cervix contains glycogen and stains brown with iodine. Non-staining areas - Schiller positive or iodine negative - may suggest CIN or MI. However, the test is not specific; benign conditions of the cervix such as ectropion, atrophy, non-malignant ulcers and columnar epithelium, also fail to stain.