BACKGROUND. Although the false-negative rate (FNR) is the most important qu
ality 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 und
etermined significance (ASCUS) as a threshold range from 17% to 61%. Source
s of error in the accuracy of this measure that must be accounted for inclu
de the FNR of the review method, differences in diagnostic thresholds betwe
en 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 val
ue in laboratories with an ASCUS+ rate of 7% can be made from interlaborato
ry rescreening of approximately 1200-1500 randomly selected normal and abno
rmal slides along with both laboratories rediagnosing without rescreening 3
00-400 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 lesio
n (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 F
NR allow creation of methods that are relatively unbiased, feasible, and te
stable and whose accuracy and precision can be determined. Cancer (Cancer C
ytopathol) 2001;93:86-92. (C) 2001 American Cancer Society..