Cervical Intraepithelial Neoplasia in the Public Health System of Bahia, Brazil: A Descriptive Time-Series Study (2014-2023)

IntroductionCervical cancer remains a major public health problem in Northeast Brazil, but the grades of histologically confirmed precursor lesions recorded in the Cancer Information System (SISCAN) have not been described for Bahia.We aimed to describe the distribution of cervical intraepithelial neoplasia (CIN) grades 1, 2, and 3 in the public health system of Bahia, Brazil, in 2014-2023 and the change in the proportion of CIN 3 after full SISCAN implementation (2017-2023), and, secondarily, the age distribution and the share of women aged 15-24 years within each grade. MethodsThis descriptive time-series study used publicly available aggregated SISCAN data from the Department of Informatics of the Brazilian Unified Health System (DATASUS).Histopathological examinations with CIN 1, 2, or 3 in women aged 15-74 years residing in Bahia were included; the unit of analysis was the examination.The proportion of CIN 3 in 2017-2023 was analyzed with quasi-binomial segmented logistic regression, using cytology examinations as denominators and a sensitivity analysis restricted to the first diagnostic specimen. ResultsA total of 9,355 CIN examinations, 2,990 (32.0%) were CIN 1, 2,072 (22.1%)CIN 2, and 4,293 (45.9%)CIN 3. The proportion of CIN 3 was 40.6% in 2017-2019 and 50.3% in 2020-2023 (odds ratio (OR) 1.48, 95% confidence interval (CI) 1.30-1.68),with no underlying annual trend once the 2020 level change was considered.This change was driven mainly by fewer CIN 1 examinations (9.5 to 6.7 per 10,000 cytology examinations; CIN 3, 10.5 to 12.1) and persisted in the sensitivity analysis.Women aged 25-44 years accounted for 71.6% of CIN 3 examinations.The share of women aged 15-24 years decreased among CIN 1 and CIN 2 examinations (Bonferroni-adjusted p<0.001 and p=0.045), but their share of cytology examinations also fell (16.0% to 11.7%), and relative to cytology volume the declines were not statistically significant. ConclusionsCIN 3 was the most frequent grade among histologically confirmed precursor lesions in the public health system of Bahia, and its proportion was higher from 2020 onward, mainly because fewer CIN 1 lesions were recorded.The decline in CIN 1 and CIN 2 among young women paralleled a decline in their screening and is hypothesis-generating: it may partly reflect HPV vaccination, but reduced screening of women under 25 years is at least as plausible.Individual-level data are needed to separate these explanations.