Accuracy of liquid-based Pap tests: comparison of concurrent liquid-based tests and cervical biopsies on 782 women with previously abnormal Pap smears.
OBJECTIVE
To evaluate the diagnostic performance of a liquid-based Pap test, the ThinPrep Pap test (TP) (Cytyc Corp., Boxborough, Massachusetts, U.S.A.), by comparing concurrent TP and cervical biopsy results on 782 patients who were referred for colposcopy because of previously abnormal conventional Pap smears (CPs).


METHODS
The ability of TP diagnoses of atypical cells of undetermined significance (ASC-US) and squamous intraepithelial lesions (SILs) to predict biopsy diagnoses of cervical intraepithelial neoplasia (CIN) was analyzed using chi2 and McNemar tests.


RESULTS
The rate of agreement between diagnoses of SIL by TP and CIN by biopsy was 74.7%. ASC-US accounted for 16.0% of TP diagnoses. ASC-US had biopsy diagnoses of CIN 1 in 60% and CIN 2/3 in 12.8% of cases. For TP diagnosis of low grade SIL, biopsy diagnoses of CIN 2/3 were found in 13.5% of cases. For TP diagnoses of ASC-US and higher, the proportions of TP and cervical biopsies in comparable diagnostic categories were statistically significant (p < 0.001), with TP having sensitivity of 89.4% and positive predictive value of 89.7% for the detection of CIN. The false positive rate for TP was 8.1%, but rescreening confirmed the presence of abnormal cells in 51 of 63 (81.0%) cases of ASC-US or higher having negative biopsies. TP had a false negative rate of 8.3% and negative predictive value of 61.3%. Rescreening showed that most (77.6%) of the false negative TP specimens failed to have abnormal cells on the slides.


CONCLUSIONS
For patients having previously detected cervical abnormalities by CP, concurrent TP demonstrated the following: (1) that it has high diagnostic accuracy for SIL, (2) that ASC-US was diagnostically equivalent to LSIL, and (3) that false negative TP for SIL can be attributed primarily to sampling rather than cytotechnologists' screening errors.
Guo
Ming
M
Department of Pathology, University of Mississippi Medical Center, Jackson, Mississippi, USA. mguo@mdanderson.org
Hu
Lulin
L
Martin
Leanne
L
Liu
Shawn
S
Baliga
Mithra
M
Hughson
Michael D
MD
D000293:Adolescent; D000328:Adult; D001706:Biopsy / Q000592:standards / Q000706:statistics & numerical data; D002584:Cervix Uteri / Q000473:pathology; D003951:Diagnostic Errors / Q000517:prevention & control / Q000706:statistics & numerical data*; D004847:Epithelial Cells / Q000473:pathology; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008875:Middle Aged; D065006:Papanicolaou Test; D011237:Predictive Value of Tests; D002583:Uterine Cervical Neoplasms / Q000175:diagnosis* / Q000473:pathology; D014626:Vaginal Smears / Q000379:methods* / Q000592:standards; D002578:Uterine Cervical Dysplasia / Q000175:diagnosis* / Q000473:pathology