[1988] Comparison of the ThinPrep® Imaging System Versus Total Manual Rescreening

Erica L Martin, Claire W Michael, Susan Shyu, Philip Bomeisl, Jay Wasman. University Hospitals Case Medical Center, Cleveland, OH

Background: The ThinPrep® Imaging System (TIS) is FDA approved for screening Papaniculou (Pap) tests using 22 fields of view (FOV) considered most abnormal by the TIS. Some controversy exists in the cytopathology community whether screening using the TIS is adequate in cases diagnosed as negative (NIL) or whether manual rescreening should be performed on all cases. Therefore, we compared the performance of screening with the TIS to total manual rescreening in NIL Pap tests.
Design: 4341 ThinPrep® Pap tests were screened using the TIS. 3340 were diagnosed as NIL on the 22 FOV selected by the TIS and subsequently manually rescreened by the same cytotechnologist. 674 cases were sent to a cytopathologist for review and final diagnosis. Biopsy follow up and Human Papilloma Virus (HPV) test results were noted if available for any Pap test with a final diagnosis of atypical squamous cells of undetermined significance (ASCUS) or above.
Results: Of the 3340 diagnosed as NIL on the TIS, 3159 (94.6%) were confirmed NIL on manual rescreen. This includes 493 of the 674 (73.1%) cytopathologist reviewed Pap tests. The false-negative rate of screening with the TIS was 5.4%. Of the 181 Pap tests that were signed out as abnormal, 147 were ASCUS, 6 were atypical squamous cells – cannot exclude high grade (ASC-H), 9 were atypical glandular cells (AGUS), 19 were low grade (LSIL), and 0 were high grade (HSIL). Biopsy follow up and HPV results are presented in table 1. Of the 148 with HPV results, 43 (29%) were positive. Of the ASCUS and HPV+ cases, only 1 cervical intraepithelial neoplasia (CIN) 2 was found on biopsy follow up.

Abnormal Pap Results
Final Diagnosis% of Abnormals (n=181)% of NIL on TIS (n=3340)Biopsy Follow UpPositive for HPV
ASCUS81.2 (147)4.47/11 CIN1, 1/11 CIN239/132
ASC-H3.3 (6)0.181/6 CIN11/6
AGUS5.0 (9)0.270/3 CIN0/5
LSIL10.5 (19)0.577/10 CIN13/5

Conclusions: Based on our data, the TIS for screening of Pap tests is accurate and reliable in NIL cases as compared to total manual rescreening. Most of the false-negative cases (81.2%) were diagnosed as ASCUS on subsequent review, with 0 HSIL cases. On patients with available follow-up, only 1 case was diagnosed as greater than CIN1 on biopsy. The HPV+ rate of ASCUS cases missed on screening with the TIS was 29.5%, suggesting that ASCUS may have been over diagnosed in some of these cases. Our results confirm that the TIS is highly accurate in excluding HSIL, negating the need for total manual rescreening.
Category: Quality Assurance

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 293, Tuesday Morning


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