Through comprehensive epidemiologic and molecular biologic studies over the last 10-15 years, it has become clear that infection with specific types of Human Papilloma Virus (HPV) is required for the development of cervical caner and its high-grade precursors (high grade SIL; CIN 2, 3). This has led to the development of sensitive molecular methods to identify HPV DNA in clinical specimens, which are available for clinical use. Such methods include Southern Blot, Hybrid Capture, PCR, and In-Situ Hybridization. The laboratories at John Muir Health are pleased to announce that we have evaluated and adopted one of these methods, In-Situ Hybridization, into our practice. Beginning early July, requests for HPV testing will be performed by this method and the results integrated into our GYN cytology (Pap smear) report.
This testing is accomplished from the same liquid based medium that is currently being used for the Pap test, so no additional specimen collection is needed. It does require, however, that the specimen collection be diligent and proper. No problem! The test performed will be for "high risk" HPV types utilizing a probe mixture designed to identify HPV types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, and 68. Because "low risk" HPV types are uncommonly found in association with high grade SIL (CIN 2, 3) and cancer, testing for these types is not considered useful and will not be performed. [The use of "low risk" HPV testing has a role in the selected instance of when a pathologist needs to determine whether a lesion that does not have the classic histological features of a condyloma acuminata is an HPV associated lesion or another type of lesion.]
The main advantage of the In-Situ Hybridization test is its ability to correlate DNA probe results with morphology. It is sensitive to 10-50 copies of target DNA in cell nucleus and does not suffer from false negatives due to insufficient cellularity in the sample. A study from authors at Columbia University Medical Center, Cleveland Clinic, and Associated Regional and University Pathologists (Diagnostic Cytopathology 2003; 29:149-55) demonstrated excellent negative predictive value (99%) and significantly better sensitivity specificity and positive predictive value than the Hybrid Capture II method.
In 2001, consensus guidelines were published on the use of HPV DNA tests in the management of women with cervical abnormalities and CIN. The American Society for Colposcopy and Cervical Pathology (ASCCP) is slated to meet again this Fall to update these consensus guidelines.
If there are any questions, please do not hesitate to contact your local client service representative or contact me directly at (925) 692-5405.