Comparison of Ex-House and In-House Cytology for the New Cervical Cancer Screening Assessment

The introduction of an organized cervical cancer screening program in Germany in 2020 changed screening algorithms and referral patterns, increasing the number of patients referred to specialized centers. This study examines the concordance between ex-house Pap smear findings and in-house colposcopy-guided cytology and relates both to colposcopy-guided biopsy and histopathological outcomes within the new screening program.

In this retrospective study, data from 3161 patients referred for colposcopy to a certified university dysplasia unit between January 2020 and May 2024 were analyzed. All patients underwent standardized assessment including Pap smear, HPV testing, colposcopy, and colposcopy-guided biopsy, with surgical treatment when indicated.

Concordance between ex-house and in-house cytology was moderate (Spearman's ρ = 0.453, p < 0.001; weighted Cohen's κ = 0.581). Compared with histology, ex-house cytology showed overdiagnosis in 252 cases (14.29%), underdiagnosis in 631 cases (35.79%), and concordant findings in 880 cases (49.91%). In contrast, in-house cytology demonstrated lower rates of overdiagnosis (183 cases, 9.48%) and underdiagnosis (495 cases, 25.65%), with agreement in 1252 cases (64.87%). HPV positivity increased with cytological severity, with HPV16 being the most prevalent genotype in high-grade lesions. Among low-grade cytological findings, CIN3+ yield differed markedly according to HPV status.

In the setting of the cervical cancer screening program, in-house cytology performed in a specialized dysplasia unit demonstrated closer agreement with histology than ex-house cytology. HPV status emerged as a key modifier of risk within low-grade cytological categories, highlighting the importance of risk-adapted triage and reassessment colposcopy in contemporary screening practice.