Volume 38 Number 12 LABMEDICINE
729The ThinPrep 2000 System (Cytyc, Marlborough, MA) and the SurePath Pap Test (BD Diagnostics, Burlington, NC), approved by the Food and Drug Administration (FDA), are based on the liquid-based preparation (LBP) for screening of cervicovaginal smears. 1 The LBP has become the primary method for screening because of the improved specimen quality and detection of squamous intraepithelial lesions. The superiority of the cell preparation technology of LBP has been attributed to the increase in specimen adequacy and the reduced proportion of specimens considered "Unsatisfactory for Evaluation." 2 However, there is a scientific debate if the application of LBP over the conventional Pap smear (CP) has improved the clinical effectiveness in cervicovaginal specimen collection and handling, and if LBP is cost beneficial. [3][4][5][6][7] To our knowledge, studies that have compared the overall performance advantage of LBP over CP have assessed only the rate of specimens considered as "Unsatisfactory for Evaluation." 7,8 We conducted a retrospective comparative caseseries study with the primary objective of evaluating the overall performance of LBP with CP, where the overall performance was defined as the sum of the adjusted proportions of unsatisfactory and rejected specimens. Adjustment for proportions was necessary because the total number of Pap screenings performed during the first phase of the study, when CP was in use, was different from the total number of Pap screenings performed after the implementation of LBP. In addition, we assessed the cited reasons by the laboratory within each category of "Rejected for Evaluation" and "Unsatisfactory for Evaluation." Finally, we compared the difference in the direct cost associated with the rejected and unsatisfactory specimens between LBP and CP.
Materials and Methods
SettingThe Henry Ford Health System (HFHS) is a comprehensive, self-contained system, organized so that persons in the system receive every level of care from preventive and primary to subspecialty services. The majority of patients at HFHS are insured through the Health Alliance Plan, a non-profit, mixed-model HMO in southeastern Michigan.When a patient is first seen at any of HFHS facilities for any reason, he or she is assigned a permanent and unique lifetime medical record number and is entered into the master patient index database that resides within a larger relational database (the corporate data store). This data store serves as the central repository for patient encounters, billing, and demographic data. Annually, more than 60,000 women undergo cervicovaginal screening at HFHS. In June 2004, the liquid-based technology (SurePath Pap Test) was fully implemented across all outpatient clinics at HFHS.Specimen collections are standardized across the system, and all specimens collected are processed and evaluated in a centralized cytopathology laboratory, affiliated with the same medical group. For specimens that are considered "Unsatisfactory for Evaluation," the laborato...