Methods of Cervical Screening

Liquid-Based Thin-Layer Specimens Versus Conventional Pap Smears

The conventional Pap smear has been the traditional method of cervical screening since the 1950s. In recent years significant efforts have been focused on improving the sensitivity of this excellent screening test. One technical improvement was the evolution of liquid based thin-layer preparations. This method offers ease of performance (a single sampling replaces the two step sampling recommended for the conventional smear) and results in significant improvement in the technical quality of the ultimate specimen that is to be reviewed. Thin-layer preparations have resulted in the following significant improvements in test performance:

1. Significant reduction in the number of unsatisfactory specimens and limited specimens caused by obscuring elements such as blood, inflammation and debris.
2. Significant reduction in the number of unsatisfactory specimens and limited specimens caused by poor fixation and inconsistent technical slide preparation.
3. Improved sensitivity (reduction of falsely negative tests) of the screening test for the detection of significant premalignant lesions of the cervix (Low grade squamous intraepithelial lesions and high grade squamous intraepithelial lesions).
4. The nature of the specimen (liquid based) allows for additional ancillary testing of the cellular material. Important additions are the use of Human Papilloma Virus DNA testing for the triage of women with the cytologic diagnosis of atypical squamous cells of undetermined significance. Other tests which may be utilized are molecular tests for the detection of sexually transmitted diseases such as chlamydia and gonorrhea.
5. The specimen is ideally suited to the screening by automated computers further improving the sensitivity of the screening test (reducing falsely negative tests).

The liquid based thin layer preparation is the recommended method for cervical screening. It should replace the traditional Pap smear in screening programs aimed at reducing the incidence of cervical cancer.

Ancillary testing: Human Papilloma Virus

Those patients in whom Atypical Squamous Cells of Undetermined Significance (ASCUS) are detected should have a HPV-DNA (Hybrid Capture 2) test performed. This is most cost effective when performed reflexively on the same liquid based thin-layer specimen demonstrating the ASCUS. Patient management can then be based on an algorithm using the results of these combined tests. This test, when performed on the thin-layer specimen that originally yielded the ASCUS diagnosis, is cost effective, sensitive and reduces the number of patients requiring more extensive and costly work-up.

Adopted MKurtinecz, 12/04
Reviewed MKurtinecz, TSp 12/04
Reviewed MKurtinecz,TSp 1/06
Reviewed MKurtinecz,TSp 5/07
Reviewed: MKurtinecz, TSp 7/08
Reviewed: MKurtinecz, TSp 8/09