Individuals reading about the human papillomavirus and the HPV vaccine will most likely come across comments pertaining to HPV genotyping. So just what is HPV genotyping and how can it be helpful?
According to the definition provided by the National Institute of Health, “A genotype is an individual's collection of genes. The term also can refer to the two alleles inherited for a particular gene. The genotype is expressed when the information encoded in the genes' DNA is used to make protein and RNA molecules. The expression of the genotype contributes to the individual's observable traits, called the phenotype.”
Even this definition can be a bit confusing, but regarding the human papillomavirus, it basically means a method of determining which strain of HPV a person may have. There are currently about 40 strains of HPV which affect the genital tract as well as the oral cavity, with 14 of those known as high risk for causing cancer.
While there are well over 100 identified strains of human papillomavirus, some which cause plantar warts and the types of warts found on the hands, most are benign. HPV6 and HPV11 are the types known to cause genital warts. Of all of these, two are known to cause the majority of cancers. These two strains are HPV16 and HPV18.
When genotyping is performed, it provides the doctor with information as to just which strains of HPV you may have and thereby the ability to assess your particular risk for developing such precancerous and potentially cancerous lesions.
Studies by the National Cancer Institute have shown that there is a 20 percent chance of developing CIN3 (the highest level of precancerous lesion before progressing to cancer) for those women with HPV16 and HPV18 even if they are shown to have negative Pap tests. Therefore, knowing if a woman has either of these two genotypes would allow for more close follow-up and evaluation than for woman who don’t. The best outcome in this situation is an earlier diagnosis and treatment and hopefully the prevention of the development of cancer at all.
The FDA recently approved Roche’s cobas HPV test which specifically identifies HPV16 and HPV18 while simultaneously testing for the other high risk strains of HPV. While the test is currently limited for use only under certain conditions, it certainly provides one more level of prevention for those which the test would be applicable.
Sources:
"Genotype - Glossary Entry - Genetics Home Reference." Genetics Home Reference - Your guide to understanding genetic conditions. N.p., n.d. Web. 16 Nov. 2011.
http://ghr.nlm.nih.gov/glossary=genotype
"STD Facts - Human papillomavirus (HPV)." Centers for Disease Control and Prevention. N.p., n.d. Web. 16 Nov. 2011.
http://www.cdc.gov/std/HPV/STDFact-HPV.htm
"HPV Genotyping Clinical Update." ASCCP is the national organization dedicated to the study, prevention, diagnosis, and management of lower genital tract disorders. N.p., n.d. Web. 16 Nov. 2011.
http://www.asccp.org/ConsensusGuidelines/HPVGenotypingClinicalUpdate/tabid/5963/Default.aspx
"cobas HPV Test â P100020." U S Food and Drug Administration Home Page. N.p., n.d. Web. 16 Nov. 2011.
http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/DeviceApprovalsandClearances/Recently-ApprovedDevices/ucm254518.htm
Reviewed November 16, 2011
by Michele Blacksberg RN
Edited by Jody Smith