Summary: Secondary screening using HPV tests in cervical cancer screening

Here is a summary of an evaluation report of HPV tests used in cervical cancer screening published by the Cancer Registry of Norway 8th December 2011.  

In the Norwegian Cervical Cancer Screening Programme women undergo primary screening with a Pap smear every three years.  Women with high risk lesions are referred for further examinations, while women with normal Pap smears have a routine Pap smear again after three years. Women with inconclusive findings undergo secondary screening.

Prior to 2005, secondary screening was carried out with a new Pap smear six months after the initial smear, and in some circumstances again after a further twelve months. From 1 July 2005 HPV tests were introduced in the secondary screening with specific guidelines.  The current report evaluates whether implementation of the different HPV-tests in secondary screening has been advantageous for cervical cancer screening in Norway. 

For this evaluation we used information obtained from the screening tests as well as the subsequent incidence of precancerous lesions and invasive cervical cancer. Results were compared for women who attended the screening before and after HPV-testing was implemented.  Results were also compared using a concurrent control group, i.e. in women with and without HPV tests in secondary screening.

Use of HPV testing in secondary screening results in:

• More women being referred to further investigation. 
• Improved distinction between low and high risk precancerous lesions
• A larger proportion of those who have abnormal cell changes during the subsequent three year period being referred for further examination.

We recommend that HPV-testing should continue as part of secondary screening in the Norwegian Cervical Cancer Screening Programme.

The following three HPV tests have been used (primarily) in secondary screening:

Hybrid Capture II (Digene), Pre Tect HPV-Proofer (Norchip AS) and Amplicor (Roche). There has been an ongoing discussion as to whether all of these HPV tests are suitable for use in secondary screening. In clinical trials Pre Tect HPV-Proofer been found to have lower sensitivity and higher specificity for detection of concurrent disease than the two other tests. The lower sensitivity can result in fewer women being referred to further investigation i.e. missed lesions. As characteristics of the tests in controlled trials are not necessarily relevant in a practical screening situation, data on these three tests were therefore analysed to obtain more relevant information.

Results: 

• Fewer women test positive on Pre Tect HPV-Proofer when compared to the other two tests:
• Fewer women tested with Pre Tect HPV-Proofer were referred for further investigation
• With Pre Tect HPV-Proofer a smaller proportion of women who were tested in the following three year period were referred for further examination
• The characteristics of these HPV tests in a practical situation appears to be similar to characteristics found in controlled studies

We recommend that the two HPV tests providing better results than
Pre Tect HPV-Proofer should be used in the Norwegian Cervical Cancer Screening Programme.