Table 1.

Definitions of time zero and exposure status used to estimate time to SIL/CIN in Kaplan-Meier and Cox analysis

Incident HPV infection?Lesion event?Analysis layout* used in Tables 2 and 3Definition of time zeroDefinition of HPV exposure
NoNo1Screening visitNegative
2Screening visitNegative
YesNo1Visit of incident HPVBy HPV type at time zero
2Screening visitHPV positivity at the last visit
NoYes and HPV−1Screening visitNegative
2Screening visitNegative
YesYes and HPV−1Visit of incident HPVType at incident HPV event
2Screening visitNegative
YesYes and HPV+1Visit of incident HPVType at incident HPV event
2Screening visitType found at incident lesion
  • * Corresponds to upper and lower sets of analyses shown in Tables 2 and 3.

  • Preenrollment visit when subject's status was ascertained as being (a) cytologically negative, (b) seronegative for HPV 16 and HPV 18 antibodies by ELISA, and (c) HPV DNA negative by a PCR assay for 14 HR-HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68).

  • HPV cleared before the occurrence of lesion.