A practical problem with calculating the false-negative rate of Papanicolaou smear interpretation by rescreening negative cases alone.
BACKGROUND
Rescreening negative Papanicolaou (Pap) smears alone is the most commonly employed method of determining the false-negative rate (FNR) or the false-negative proportion for a laboratory. Acceptable FNRs have been proposed, and the number of slides needed to be rescreened to demonstrate a statistically significant difference in FNRs has been determined. The authors sought to determine the range of FNRs this method can measure and, by implication, the value of this method.


METHODS
A literature review and an analysis of the FNRs this method can generate was performed.


RESULTS
If one assumes that the FNR of review is the same as that of initial screening, the maximum measured FNR is only 25%, even with a true FNR of anywhere from 0-100%. In fact, as a laboratory's FNR increases over 50%, the measured FNR decreases back to zero. This range of FNRs corresponds very closely to the published range of FNRs of 1.6-28%. Because many authorities believe that 5% may be the lowest achievable FNR, the entire possible range of measured FNRs is only 5-25%. In this setting, a statistically significant difference of 20% is meaningless, and a statistically significant difference of 10% can only be achieved by laboratories with an initial FNR of less than 15%, and actual changes in FNR that are much greater than 10%.


CONCLUSIONS
FNRs determined by review of negative smears without abnormal smears generate unreliable and potentially seriously misleading results. Current methodologies exist for more accurately determining the FNR of Pap smear screening by incorporating abnormal smears into the review process. There is little justification for further review of negative Pap smears alone as a method for determining the FNR of a laboratory. Cancer (Cancer Cytopathol)
Renshaw
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Department of Pathology, Baptist Hospital of Miami, Miami, Florida 33176, USA.
D005188:False Negative Reactions; D005260:Female; D006801:Humans; D007753:Laboratories / Q000592:standards; D065006:Papanicolaou Test; D010336:Pathology / Q000592:standards; D011785:Quality Assurance, Health Care; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014626:Vaginal Smears / Q000145:classification / Q000592:standards / Q000706:statistics & numerical data*