Low Proportion of False-Negative Smears in the Finnish Program for Cervical Cancer Screening

Abstract

Background: We assessed the performance and validity of cytology in the Finnish screening program by considering high-grade neoplasia and cervical cancer (CIN3+) rates as detected in the program and by reevaluating cases observed after a negative screening test.Methods: This retrospective study included 915 screen-detected CIN3+ cases and 421 cases observed after a negative screen. Randomized and blinded reevaluation of potential false-negative screening tests covered 345 archival case smears from women without a referral to colposcopy, as well as 689 control smears for estimating performance and validity measures.Results: The false-negative rate at the cutoff of low-grade squamous intraepithelial lesion or worse was 35% (95% confidence interval, 30-40%). In the subpopulation with original screening result of Pap I, the false-negative rate was 23% (18-28%). Sensitivity of screening laboratory rereading for detecting low-grade lesions or worse as atypical was 75% (67-82%) and specificity 93% (91-94%). Reproducibility of specific cytologic diagnoses was only fair. False negatives constituted 11% of all CIN3+ diagnoses in the screened population; those false negatives with an original Pap I screening result constituted 5%.Conclusions: Although screen failures in the form of diagnostic false negatives occur within the Finnish screening program, their effect on cancer incidence is fairly small and cannot be readily decreased without sacrificing the high specificity of screening or without high incremental costs. Feedback for the screening laboratories is needed, however, to improve the reproducibility of cytologic diagnoses to optimize the burden of intensified follow-up and treatment of precancerous lesions. Cancer Epidemiol Biomarkers Prev; 19(2); 381-7. ©2010

Large performance variation does not affect outcome in the Finnish cervical cancer screening programme

“…An explanation might be that on diagnosis of cervical cancer, the treating hospital often requests any previous smears, sometimes failing to return them to the screening laboratory. However, overall validity measures and false negative rates did not vary with the eventual histological diagnosis 2 …”

“…Cervical screening based on conventional cytology has been effective in reducing incidence of and mortality from cervical cancer but requires a high level of screening programme organization for good results 1 . Cytology itself often suffers from low reproducibility and interobserver agreement 2–5 . In order to achieve and maintain high effectiveness, continuous quality assurance of a screening programme is essential 1 .…”

“…1 Cytology itself often suffers from low reproducibility and interobserver agreement. [2][3][4][5] In order to achieve and maintain high effectiveness, continuous quality assurance of a screening programme is essential. 1 Key performance indicators, including attendance, referral and cervical intraepithelial neoplasia (CIN) detection rates, are readily available from screening records of good quality.…”

False-Negative Rate of Papanicolaou Testing: A National Survey from the Thai Society of Cytology

“…A survey among US-based university hospital laboratories reported a 10-31% FNR [20] . A more recent examination by Lonnberg et al [21] found an even wider range of 15-63%. As reducing the FNR to below 5-10% is thought to be extremely difficult [22] , a 10-20% FNR is considered good or fair [15,19] .…”

“…However, random rescreening may also be employed as an external quality control measure. A recent study based on the clinical outcomes conducted by the national cervical cancer screening program in Finland found a 35% FNR at the cutoff of L-SIL or worse [21] . Our average FNR over 5 years was 13.8%, and there were 2 years in which the rate was lower than 10%.…”