title: Duration and clearance of anal human papillomavirus (HPV) infection among women: the Hawaii HPV cohort study.
abstract: BACKGROUND
  The association of anal cancer with human papillomavirus (HPV) infection is well established; however, little is known about the epidemiology of anal HPV in healthy women. We investigated patterns of duration and clearance of anal HPV infection in a cohort of healthy women in Hawaii.
  
  
  METHODS
  Viral and nonviral determinants of anal HPV clearance were examined in a longitudinal cohort study of 431 sexually active women. At baseline and at 4-month intervals, interviews were conducted and cervical and anal cell specimens were obtained for detection of HPV DNA.
  
  
  RESULTS
  Of the 431 women, 50% experienced a total of 414 incident anal HPV infections, reported at 1 clinic visits from baseline through a follow-up period of average duration of 1.2 years. Of these infections, 58% cleared during follow-up. The clearance rate for a high-risk anal infection was 9.2 per 100 woman-months (95% confidence interval [CI], 6.9-11.9 per 100 woman-months), with a median duration of 150 days (95% CI, 132-243 days). The slowest clearing high-risk HPV types were HPV-59 (median clearance time, 350 days) and HPV-58 (median clearance time, 252 days). The median clearance times for HPV-16 and HPV-18, the predominant types associated with anal cancer, were 132 days and 212 days, respectively. Nonviral factors that delayed clearance of anal HPV included douching, long-term tobacco smoking, and anal sex.
  
  
  CONCLUSIONS
  The majority of anal HPV infections resolve in a relatively short time. Although anal HPV is commonly acquired in healthy women, its rapid clearance suggests limited efficacy of HPV testing as an anal cancer screening tool.
authors.affiliation: Cancer Research Center of Hawaii, University of Hawaii, Honolulu, Hawaii 96813, USA. yshvetso@crch.hawaii.edu
authors.forename: Yurii B
authors.initials: YB
authors.lastname: Shvetsov
authors.forename: Brenda Y
authors.initials: BY
authors.lastname: Hernandez
authors.forename: Katharine
authors.initials: K
authors.lastname: McDuffie
authors.forename: Lynne R
authors.initials: LR
authors.lastname: Wilkens
authors.forename: Xuemei
authors.initials: X
authors.lastname: Zhu
authors.forename: Lily
authors.initials: L
authors.lastname: Ning
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Killeen
authors.forename: Lori
authors.initials: L
authors.lastname: Kamemoto
authors.forename: Marc T
authors.initials: MT
authors.lastname: Goodman
mesh_terms: D000328:Adult; D000368:Aged; D001003:Anal Canal / Q000473:pathology / Q000821:virology*; D002584:Cervix Uteri / Q000821:virology; D015331:Cohort Studies; D005260:Female; D006254:Hawaii / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D027383:Papillomaviridae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D030361:Papillomavirus Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000821:virology*; D011349:Proctitis / Q000188:drug therapy / Q000453:epidemiology* / Q000821:virology*; D013997:Time Factors