Temporal Trends in Cytological Sample Adequacy and High-Grade Cervical Lesion Detection in the Brazilian Amazon: A Decade-long Analysis (2013-2023)

Background Cervical cancer is a significant public health burden worldwide, particularly in low- and middle-income countries. In Brazil, the Amazon region experiences disproportionately high mortality compared with the national average. This study evaluated a decade of cervical cancer screening in Pará State (2013–2023), focusing on cytology quality and detection of high-grade lesions. Methods A retrospective analysis was conducted using 1,793,106 cervical cytology tests recorded in the Brazilian Cervical Cancer Information System (SISCOLO) from 2013 to 2023. The main outcomes were sample adequacy, classified according to Bethesda criteria, and detection of high-grade squamous intraepithelial lesions (HSIL+). Temporal trends were assessed using Joinpoint regression, while associations between sample adequacy and HSIL + detection were analyzed with logistic regression, adjusting for annual test volume. Results Overall, 96.1% of samples were satisfactory, 1.1% unsatisfactory, and 2.8% rejected. Sample adequacy exceeded 98% in the pre-pandemic period but declined to 96.4% in 2023. The HSIL + detection rate increased from 0.33% in 2013 to 0.57% in 2023, representing a 73% rise. Logistic regression revealed a significant association between unsatisfactory samples and HSIL + detection (OR = 1.8, 95% CI: 1.5–2.1). Joinpoint regression showed a 6.1% annual increase in HSIL + detection between 2013 and 2019, a 51% reduction in 2020, and a 4.8% annual increase from 2021 to 2023. Conclusions Screening coverage and quality improved over the decade, but service disruptions during the COVID-19 pandemic revealed systemic vulnerabilities. Achieving WHO elimination targets will require sustained investment in primary care, laboratory capacity, and equitable screening strategies tailored to the Amazonian context.