Table 3.

The monthly duration and persistence of HPV-6, HPV-11, HPV-16, and HPV-18 infections up to the time of diagnosis of CIN or clearance

Mean duration,* mo (95% CI)Lower bound mean duration,* mo (95% CI)Upper bound mean duration,* mo (95% CI)Median duration, mo (95% CI)Proportion persistent at 12 mo (95% CI)Proportion persistent at 24 mo (95% CI)Proportion persistent at 36 mo(95% CI)
HPV-6 (n = 103)8.4 (7.5-9.3)5.8 (5.0-6.7)11.0 (10.0-11.9)6.2 (6.1-7.1)26.0% (16.8-35.3)0.0% (—)0.0% (—)
HPV-11 (n = 13)8.1 (5.5-10.7)4.7 (2.5-6.9)11.4 (8.2-14.6)6.5 (5.7-11.9)12.5% (5.7-26.2)0.0% (—)0.0% (—)
HPV-16 (n = 142)13.9 (12.1-15.7)11.9 (10.1-13.7)16.1 (14.2-18.0)11.7 (9.8-14.3)47.2% (38.0-56.4)15.8% (7.9-23.7)0.0% (—)
HPV-18 (n = 62)14.9 (11.9-18.0)12.4 (9.3-15.5)17.4 (14.4-20.5)12.4 (10.7-16.3)52.9% (39.3-66.5)16.3% (4.9-27.8)8.2% (4.9-13.6)
  • * Because the individual observation with the longest follow-up time was censored for the analysis of HPV-18 infections, the mean duration of infection is underestimated.

  • The lower bound for mean duration was estimated assuming that HPV infections began one fourth of the way between the initial positive test and the last prior negative cervical swab and ended one fourth of the way between the last positive test and the first subsequent negative cervical swab. For the upper bound, the cut point was changed from one fourth to three fourths, with the midpoint used for the primary analyses.