A Primer on HPV Types
How many types of HPV are there?
There are more than 100 types of HPV. They usually don't cause any problems. However, when they do, the most frequent effect is the common wart, such as those found on the hands and feet.
About 30 HPV types are spread through genital contact. Each is “named” with a number, in the order of their discovery. In addition, they are divided into two groups:
"Low-risk" types of HPV
There are about 12 types of HPV that are called "low risk" because they cannot cause cervical cancer. They can, however, cause genital warts or very minor cell changes on the cervix. These low-risk types of HPV are known by the numbers 6, 11, 40, 42, 43, 44, 53, 54, 61, 72, 73 and 81. Types 6 and 11 – which are linked to about 90 percent of genital warts – are the most common.
"High-risk" types of HPV
There are more than a dozen types of "high-risk" HPV that can cause abnormal cells to form on the cervix. These abnormal cell changes may gradually develop into cervical cancer if not removed. The 13 types of high-risk HPV that are of most concern are known by the numbers 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 and 68. Types 16 and 18 are the most dangerous, since they cause about 70 percent of cervical cancers. In one study, the National Cancer Institute found that about 10 percent of women with HPV type 16 or 18 developed advanced, pre-cancerous cervical disease (CIN 3) within three years (compared to just 4 percent of women with any type of HPV), and 20 percent did so in 10 years (compared to 7 percent).
What types does the HPV vaccine protect against?
Gardasil®, the HPV vaccine developed by Merck, is designed to protect against HPV types 16 and 18 – which cause about 70 percent of cervical cancers. In addition, it protects against the two most common that cause genital warts – 6 and 11.
What types does the digene HPV Test detect?
The digene HPV test, the first FDA-approved HPV test, tells you and your healthcare provider whether you have one or more of the 13 most important high-risk types of the virus-16,18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 and 68. (Although QIAGEN also makes a test for low-risk HPV types, its routine use is not recommended in medical guidelines or reimbursed by insurance.)
Currently, the digene HPV Test does not tell you specifically which high-risk type(s) of the virus you have. However, under existing medical guidelines, the extra exams and other follow-up care you should get are the same no matter what type of high-risk HPV you have.
That may change in the future. QIAGEN and other companies are developing additional, follow-up tests that could, for example, determine whether you have HPV 16 and/or 18 – the types that cause about 70 percent of cervical cancers.