2008, Volume 19, Number 2
Changes in Human Papillomavirus Testing
Danny Wiedbrauk, PhD
Human Papillomavirus (HPV) is the most common sexually transmitted infection in the United States with an estimated 6.2 million new cases each year (1). Of these, 74% occur among those aged 15-24 years. Statistical modeling studies suggest that more than 80 percent of sexually active women will have acquired genital HPV by their 50th birthday (2).
There are about 100 different HPV types and approximately 30 types are spread through genital contact. HPV types are designated by number and genital types are classified as either "low-risk" or “high-risk.” Low risk HPV types cause genital warts and high-risk HPV types can cause cervical cancer.
"High-risk" types. There are about 15 high-risk HPV types and 13 of the most prevalent high-risk types are detected by the Hybrid Capture 2 (HC2) test used by Warde Medical Laboratory. In one high risk cervical cancer study, the two remaining high-risk types had a combined incidence of 0.3% (3). HPV types 16 and 18 cause about 60-70 percent of cervical cancers (4, 5). One National Cancer Institute study found that about 10 percent of women with HPV type 16 or 18 developed advanced, pre-cancerous cervical disease (CIN 3) within three years and 20 percent did so in 10 years. Only four percent of patients with high risk HPV types other than 16 or 18 developed CIN 3 within three years and 7% developed CIN 3 within 10 years (6). Types 16 and 18 are included in the quadravalent HPV vaccine.
“Low-risk” types. About 12 HPV types are classified "low risk" because they do not cause cervical cancer. Instead, these HPV types cause genital warts and/or minor cell changes on the cervix. Five low-risk HPV types (6, 11, 42, 43, and 44) are detected by the HC2 assay. Types 6 and 11 are included in the quadravalent HPV vaccine because they cause about 90 percent of all genital warts (7). Low-risk HPV types are spread in the same way as high-risk HPV – through genital skin-to-skin contact. Unlike high-risk HPV types, low risk HPV types do not cause cervical cancer and it is not unusual for women with genital warts to have a normal PAP test and a negative HPV high risk test.
Low-risk HPV DNA testing has little clinical utility because genital warts are usually diagnosed by physical examination. This lack of utility also means that many third-party payers do not reimburse for low-risk HPV testing.
Test Changes. On August 18, 2008 Warde Medical Laboratory will discontinue the combined high-risk/low-risk HPV test (test codes: HPVS, 30-90310). A new low-risk HPV test option (HPVLR, 30-90340) is available for those unusual instances where HPV low risk testing is desired. Routine low risk testing is discouraged.
- Weinstock H, Berman S, Cates W Jr. Sexually transmitted diseases among American youth: incidence and prevalence estimates, 2000. Perspect Sex Reprod Health 2004;36:6-10.
- Myers ER, McCrory DC, Nanda K, Bastian L, Matchar DB. Mathematical model for the natural history of human papillomavirus infection and cervical carcinogenesis. Am J Epidemiol 2000;151:1158-71.
- Franco EL, Villa LL, Sobrinho JP, Prado JM, Rousseau M-C, Desy M, Rohan TE. Epidemiology of acquisition and clearance of cervical human papillomavirus infection in women from a high-risk area for cervical cancer. J Infect Dis 1999;180;1415-1423.
- Clifford GM, Smith JS, Plummer M, Munoz N, Franceschi S. Human papillomavirus types in invasive cervical cancer worldwide: a meta- analysis. Br J Cancer 2003;88:63-73.
- Bosch FX, de Sanjose S. Chapter 1: Human papillomavirus and cervical cancer — burden and assessment of causality. J Natl Cancer Inst Monogr 2003;31:3-13.
- Khan MJ, Castle PE, Lorincz AT, Wacholder S, Sherman M, Scott DR, Rush BB, Glass AG, Schiffman M. The elevated 10-year risk of cervical neoplasia in women with human papillomavirus (HPV) type 16 or 18 and the possible utility of type-specific HPV testing in clinical practice. Journal of the National Cancer Institute, 2005;97(14):1072-1079.
- Greer CE, Wheeler CM, Ladner MB, Beutner K, Coyne MY, Liang H, Langenberg A, Yen TS, Ralston R. Human papillomavirus (HPV) type distribution and serological response to HPV type 6 virus-like particles in patients with genital warts. J Clin Microbiol 1995;33:2058-63.