A more accurate measure of the false-negative rate of Papanicolaou smear screening is obtained by determining the false-negative rate of the rescreening process.
BACKGROUND
The false-negative rate (FNR), or fraction, of Papanicolaou (Pap) smear screening has been proposed as a useful quality assessment measure. The FNR should account for the FNR of the rescreening process itself. The authors measured the FNR of the rescreening process by rescreening a set of abnormal smears.


METHODS
A randomly selected group of negative (150) and abnormal (91) smears were rescreened in a blinded fashion. A diagnosis of atypical squamous cells of undetermined significance (ASCUS) or worse was used as a positive (abnormal) result. All discrepancies were confirmed by consensus review. The true FNR of screening Pap smears was calculated as: true FNR = calculated FNR/(1-FNR of rescreening).


RESULTS
When rescreened, 17 originally negative cases were interpreted as ASCUS and 5 as unsatisfactory. Twenty-three originally abnormal cases (22 ASCUS and 1 low grade squamous intraepithelial lesion) were interpreted as negative. After consensus review, only 1 of the originally negative cases was believed to be ASCUS and 1 unsatisfactory; 18 of the 23 originally abnormal cases were believed to be rescreening errors and 5 of the 23 originally abnormal cases were believed to be false-positives. The FNR of Pap smear screening as traditionally calculated was 6.1%, which was slightly less than the laboratory's usual FNR. The FNR of review screening was 20.9%. The true FNR of Pap smear screening was 7.8% and the false-positive rate was 0.6%.


CONCLUSIONS
The FNR of rescreening is not insubstantial. It can and should be measured by rescreening abnormal smears, and when taken into account yields a more accurate measure of the FNR of Pap smear screening.
Renshaw
A A
AA
Department of Pathology, Brigham & Women's Hospital, Boston, Massachusetts 02115, USA.
DiNisco
S A
SA
Minter
L J
LJ
Cibas
E S
ES
D002278:Carcinoma in Situ / Q000175:diagnosis*; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis*; D003627:Data Interpretation, Statistical; D003951:Diagnostic Errors / Q000706:statistics & numerical data; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D065006:Papanicolaou Test; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis*; D014626:Vaginal Smears / Q000706:statistics & numerical data*