HPV is associated with cancers of the cervix, anus and oropharynx. Few studies have simultaneously looked at HPV infection in all three anatomical sites in healthy 18-26 year old Thai women. Thai girls and women are not yet routinely vaccinated for HPV. Information on HPV DNA at these sites and seropositivity to HPV 16 and 18 is needed to inform the design of HPV vaccination programs for 18-26 year old women in Thailand.
We recruited 150 healthy HIV-negative women age 18 to 26 with no more than 5 lifetime partners for an HPV vaccine study in Bangkok, Thailand. Cervical HPV DNA was sought using the Cobas HPV test and Linear Array HPV genotyping test. Anal and oral compartments were tested using the Cobas HPV test followed by Linear Array testing of Cobas-positive specimens. A sexual history, socio-demographic information and serum for a pseudovirion-based neutralization assay (PBNA) to detect antibodies to HPV 16 and 18 were also collected at baseline. Fisher’s exact test and logistic regression were used to determine if demographic or other health and sexual risk factors were associated with high-risk HPV (HR-HPV) infection in the anus.
Of the 150 Thai women (median age=23 years, median age of sexual debut=19 years), 41/150 (27.3%) women were positive for cervical HR-HPV DNA and 30/150 (20.0%) were positive for anal HR-HPV DNA. Only one participant had HPV (HPV 53) detected in the oropharynx. Anal HPV 16 and 18 DNA were present in 8/150 (5.3%) and 5/150 (3.3%) participants, respectively, and 12/13 (92.3%) with anal HPV 16 or 18 infection had concordant infection in the cervix. 28/150 (18.7%) and 6/150 (4.0%) women were HPV 16- and HPV 18-seropositive, respectively. In bivariate analysis, anal HR-HPV infection was associated with cervical HR-HPV infection (p<.001), increased number of lifetime partners (p=.007) and past smoking (P=.05), but not reported history of anal sex. In multivariable analysis, only cervical HR-HPV infection was associated with high-anal HR-HPV infection (OR 14.8, 95% CI 5.4-40.5; P<.001) after adjusting for number of lifetime partners and past smoking.
Anal HR-HPV infection is common among HIV-negative women in Thailand and these women may be at increased risk of anal cancer in the future. Oral HPV infection was uncommon. There was a high degree of concordance between anal and cervical HPV 16 and 18 infection. Anal HR-HPV infection was associated with cervical HR-HPV infection, but not with history of reported anal sex. Our data suggest that many of these infections may be acquired through spread from the cervix. HPV vaccination may still benefit most 18 to 26 year-old Thai women.