Table 1.

 Size of study groups

Type of episode	Mean (SD) age at primary smear test (years)	No of episodes	No of woman years at risk*	No of cases*
CIN with completed negative follow-up test results†	35.9 (8.6)	38 956	56 956	20‡
Normal primary smear test results	41.9 (10.9)	7 096 816	25 020 697	1613

CIN=histologically confirmed cervical intraepithelial neoplasia.

*Only non-censored woman years at risk are included.

†When episodes of CIN with completed negative follow-up results were considered only if the timing of follow-up tests followed recommendations (side analysis), 13 cases of cervical cancers were diagnosed in 38 040 woman years within 23 415 episodes that started at an mean age of 36.0 (SD 8.6) years.

‡One woman was treated for adenocarcinoma in situ.