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Human Papillomavirus DNA Hybrid Capture

Human papillomavirus (HPV) is a DNA virus in the papovavirus family. Infection of the female genital tract is associated with genital condyloma acuminata, condyloma plana, Bowenoid papulosis and cervical, vaginal, and vulvar intraepithelial neoplasia and carcinoma. Although there are reports of vertical and fomite transmission, HPV is most commonly sexually transmitted. Cervical cancer develops in about 1% of HPV-infected women and cervical dysplasia in about 15%.

• 99% of cervical cancers have been associated with HPV
• HPV 16 & 18 account for 2/3 of cervical cancers regardless of geography
• HPV 16 positivity has a relative risk of 434 for cancer, other types have RR >100
• >80% of college aged females have been exposed to HPV
• Majority of females are infected with high risk HPV
• Most have a transient infection that causes a low grade cervical lesion
• Very few women remain persistently infected & HPV DNA becomes negative
• 50% clear infection within 6 mos and 90% clear infections within 2 y
• 10% develop HPV persistence & are at risk for cancer; develop CIN 3 within 76 mos
• Studies in Haiti suggest that HPV 16 & 58 are most likely to be persistent
• There is a pronounced drop in infection rate between 30 & 35 years, so women should not be screened before the age 30

Over 100 HPV genotypes have been identified to date by DNA hybridization. HPV Digene II is much more reliable than PAP smear & has decreased lab to lab variability. Research suggests that viral typing may prove useful as an adjunct to the PAP smear in identifying women who may be at risk for cervical intraepithelial neoplasia.

Obstetricians have been reluctant to adopt HPV screening for the following reasons:

• If both tests are negative, current guidelines recommend not repeating the tests for 3 years; patients may be lost to follow-up
• HPV positive & cytology negative results produce patient anxiety
• Guidelines call for repeating HPV in 6-12 mos, but patients don’t want to wait for confirmation
• The large number of HPV positives will overwhelm colposcopy resources

HPV genotypes can be classified according to their malignant potential:

For diagnostic purposes, the Digene hybrid capture assay may be performed on a cervical swab or biopsy specimen. Bloody specimens may give false-negative results, as will low levels of infection below detection levels of the assay. Types of HPV other than those listed above will not be detected.

Reference value is negative. Positive results are reported as one of two HPV groups; low risk (types 6, 11, 42, 43, 44), or intermediate/high risk (types 16, 18, 31, 33, 35, 45, 51, 52, 56). The test does not distinguish viral types within the two probe groups. Clinical management needs to be based on HPV high risk types; there is no clinical utility for low risk types.

Cervical swab specimens must be collected in Digene HPV Specimen Collection Kit or Digene specimen transport medium. Refrigerate after collection.

Cervical biopsies should consist of 3 mm tissue placed into 1.0 mL of Digeneâ specimen transport medium. Specimen must be sent frozen on dry ice.

An HPV vaccine against types16&18 has been developed. The vaccine should be administered before females become sexually active. The impact of the vaccine on HPV prevalence will probably not be seen for 20 to 30 years after its introduction.