Table 4.

The monthly duration and clearance of HPV-6, HPV-11, HPV-16, and HPV-18 infections with censoring at the time of treatment

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 cleared at 12 mo (95% CI)Proportion cleared at 24 mo (95% CI)Proportion cleared at 36 mo (95% CI)
HPV-6 (n = 103)9.3 (8.4-10.2)6.3 (5.4-7.3)12.2 (11.2-13.1)6.8 (6.2-10.8)66.5% (56.3-76.7)98.2% (97.9-98.5)98.2% (97.9-98.5)
HPV-11 (n = 13)8.4 (5.4-11.4)5.6 (3.3-7.8)11.7 (8.1-15.3)6.5 (5.7-11.9)85.4% (66.0-94.2)100.0% (—)100.0% (—)
HPV-16 (n = 142)18.2 (15.9-20.6)15.1 (13.0-17.3)21.3 (18.8-23.8)15.6 (12.1-18.2)40.1% (30.8-49.4)69.0% (58.9-79.2)85.3% (75.0-91.5)
HPV-18 (n = 62)16.4 (13.1-19.6)13.6 (10.2-17.0)19.1 (16.0-22.3)12.8 (11.7-17.5)41.5% (27.4-55.7)77.7% (64.0-91.4)91.1% (84.6-94.9)
• * Because the individual observation with the longest follow-up time was censored for the analyses of HPV-6, HPV-16, and 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.