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An accurate and precise methodology for routine determination of the false-negative rate of Papanicolaou smear
1Department of Pathology, Baptist Hospital of Miami, Miami, Florida, USA.
Background:
Although the false-negative rate (FNR) is the most important quality control measure for Papanicolaou smear screening, accurate, precise, and feasible methods for determining this value are lacking.
Methods:
The author undertook an analysis and review of the literature.
Results:
The best estimates of the FNR using atypical squamous cells of undetermined significance (ASCUS) as a threshold range from 17% to 61%. Sources of error in the accuracy of this measure that must be accounted for include the FNR of the review method, differences in diagnostic thresholds between the original diagnostic method and the review method, and differences in diagnostic accuracy between the original diagnostic method and the review method. Statistically precise (valid to within 10%) measurement of this value in laboratories with an ASCUS+ rate of 7% can be made from interlaboratory rescreening of approximately 1200-1500 randomly selected normal and abnormal slides along with both laboratories rediagnosing without rescreening 300-400 benign cellular change and ASCUS slides to determine the difference in diagnostic threshold. Consensus for each slide is not required with this method. Changing the threshold to low grade squamous intraepithelial lesion (best estimate FNR, 14-58%) requires review of significantly more slides to achieve the same statistical level of precision.
Conclusions:
Detailed analysis of the sources of error in determining the FNR allow creation of methods that are relatively unbiased, feasible, and testable and whose accuracy and precision can be determined.
Insights
Accurate methods for determining the false-negative rate (FNR) in Papanicolaou smear screening are needed. This review analyzes errors and proposes feasible approaches for precise FNR measurement in cervical cancer screening.
Area of Science:
- Gynecologic Pathology
- Cytopathology Quality Assurance
Background:
- The Papanicolaou (Pap) smear is crucial for cervical cancer screening.
- Accurate determination of the false-negative rate (FNR) is essential for quality control but lacks standardized methods.
Purpose of the Study:
- To review literature and analyze sources of error in FNR determination for Pap smear screening.
- To propose feasible and testable methods for accurate and precise FNR measurement.
Main Methods:
- Literature analysis and review.
- Evaluation of error sources affecting FNR accuracy (e.g., review method FNR, threshold differences).
Main Results:
- Estimated FNR ranges from 17% to 61% using atypical squamous cells of undetermined significance (ASCUS) as a threshold.
- Statistically precise FNR measurement (within 10%) requires rescreening ~1200-1500 slides and rediagnosing ~300-400 slides.
- Adjusting the threshold to low-grade squamous intraepithelial lesion increases slide review requirements.
Conclusions:
- Understanding error sources enables the development of unbiased, feasible, and testable FNR determination methods.
- Proposed methods allow for determined accuracy and precision in quality control for Pap smear screening.
