Pap test and a new biomarker-based technology for enhancing the visibility of abnormal cells


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Citation: Journal of Clinical Oncology, 2004 ASCO Annual Meeting Proceedings (Post-Meeting Edition). Vol 22, No 14S (July 15 Supplement), 2004: 9561
Authors: N. S. Markovic, O. Markovic, J. Sundeen, W. Smith, S. N. Markovic, R. CAP-PAP Test for Cervical Cancer Screening Study Group; BioSciCon, Inc., Rockville, MD; Diagnostic Pathology Services, Inc., Clarksburg, MD; Department of Pathology, Suburban Hospital, Bethesda, MD; Mayo Clinic, Rochester, MN
Abstract: BACKGROUND: At ASCO 2001, we introduced the Cervical Acid Phosphatase – Papanicolaou (CAP-PAP) test as a new, biomarker-driven technology for detection of abnormal cervical cells on Pap smears. Since this report, we conducted two clinical trials to assess the value of this test for cervical cancer screening in general (N=1,500) and a high-risk population (N=500). This technology is commercially available as the MarkPap™ Research Kit (BioSciCon, Inc., Rockville, MD, USA). METHODS: Multicenter, random assignment, assessors blinded, split sample, concurrent control 3-group (test and two controls [Pap smears and ThinPrep thin layers] clinical trial was conducted on 1,500 specimens obtained from eligible subjects coming for regular Pap test. Specimens collected in PreservCyt® and transferred onto microscopic slides using the ThinPrep Processor 2000 were split in two samples before processing. Specimens obtained with cervical epithelium abrading devices, were split by the physician in two samples (smears). Primary efficacy endpoints were the portion of detected abnormal samples and the portion of false negative readings. Accuracy was measured against a cytology standard (association or adjudication).

Comparison between test and control groups Subgroup A:
MPT vs. ThP
Subgroup B:
MPT vs. Pap smears
MPT vs. ThP MPT vs. Pap
Number of samples 348 1,039 25% 75%
Association 0.86 [Y+, or Y-] 0.83 [Y+, or Y-] Consensus standard
Discrepancy 0.14 [N+-, or N-+] 0.17 [N+-, or N-+] Adjudicated standard
Abnormal samples 0.097 0.103 0.157 0.049 [Pe -Ps] ≤ δ* Pe ≤ Ps+δ
False negatives - - 0.04 0.09 - Pe < Ps - δ
Sensitivity 0.45 0.60 0.837 0.513 [Pe-Ps] ≤ δ Pe > Ps+δ
Specificity 0.95 0.98 0.948 0.995 [Pe-Ps] ≤ δ [Pe-Ps] ≤ δ

CONCLUSION: This data suggests that the new technology is more sensitive (with equivalent specificity) than either conventional Pap smear or ThinPrep Pap test. However, when specimens were collected in PreservCyt®, due to alcohol inhibition of the enzyme, this sensitivity was reduced. This work was supported in part by NCI, NIH, via SBIR Phase-1 and Phase-2 grants: 1 R43CA086767-01, and 2-R44CA086767-02.

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