Table 2.

Incidence of squamous cervical lesions (SIL or CIN) and mean time to first lesion in cohort analyses based on different exposure time and outcome definitions

Time zero* defined atHPV exposure status defined atOutcome definitionHPV exposure statusNo. womenWomen-months at riskIncident lesions§Mean time to lesion (mo)
Actuarial (95% CI)Crude (lesion only; 95% CI)
Screening or 1st HPV infection eventScreening or 1st HPV infection eventCytology onlyNegative25610,816.4566.4 (65.4-67.3)29.7 (5.5-53.8)
Only LR-HPV types33868.5454.5 (47.5-61.6)10.1 (0.6-19.7)
HR-HPV, non-16/181112,886.03044.8 (40.2-49.4)18.6 (13.7-23.6)
HPV 16 or 18571,532.41944.4 (37.4-51.4)10.2 (6.3-14.2)
Biopsy + cytologyNegative25610,908.7267.1 (66.7-67.5)55.6 (37.7-73.6)
Only LR-HPV types33868.5454.5 (47.5-61.6)10.1 (0.6-19.7)
HR-HPV, non-16/181133,095.72846.4 (42.0-50.7)20.3 (15.3-25.3)
HPV 16 or 18591,620.52143.3 (36.4-50.1)12.8 (8.4-17.2)
ScreeningLast visit or 1st abnormality or lesion eventCytology onlyNegative33815,511.1967.4 (66.6-68.2)34.9 (19.2-50.6)
Only LR-HPV types251,037.6852.5 (43.7-61.2)26.8 (11.5-42.1)
HR-HPV, non-16/181003,957.04548.6 (44.1-53.0)31.3 (26.0-36.5)
HPV 16 or 18592,120.83243.4 (37.6-49.1)29.1 (23.3-34.9)
Biopsy + cytologyNegative34315,753.81067.3 (66.5-68.1)41.2 (27.6-54.8)
Only LR-HPV types251,118.5756.3 (49.2-63.4)35.3 (20.4-50.2)
HR-HPV, non-16/18953,895.64050.6 (46.3-54.9)33.8 (28.2-39.3)
HPV 16 or 18592,232.52946.4 (41.0-51.8)33.1 (27.4-38.8)
  • * For the calculation of time to lesion event. The exit visit was the one with an incident lesion (date of incident SIL/CIN), or the last visit, for women who did not develop any lesions during follow-up. See Table 1 for details.

  • By design, at the screening visit, all women were HR-HPV negative. For the first set above, HPV exposure status was based on the type found in the first HPV infection event or, if negative up to exit visit, on the status at screening. For the second set, exposure status was based on the last observation for each woman or on the HPV type associated with the incident lesion during follow-up. See Table 1 for details.

  • Does not take into account changes in status during follow-up. LR-HPV events at screening were not included as exposure outcome. For the second set, HPV-negative women may have been HPV positive at a previous instance during follow-up but cleared their infection before exit (last visit without lesion event or first instance of lesion event). See text for details on categories of HPV positivity.

  • § The first recorded abnormality; subsequent ones not considered.

  • Whether it was based on the actuarial analysis (Kaplan-Meier estimates), which accounts for censoring, or simply restricted only to those who developed lesions.

  • Hierarchical use of cytology and biopsy diagnoses: cytology results replaced by biopsy results when biopsy was done.