Gynecologic cytology on conventional and liquid-based preparations: a comprehensive review of similarities and differences.

Liquid-based preparations (LBPs) have largely replaced conventional Papanicolaou smears (CPS) for cervical samples in the United States and in many other industrialized countries. The two FDA-approved LBP currently in use include ThinPrep (TP), (Hologic Inc., Bedford, MA) and SurePath (SP), (BD Diagnostic, Burlington, NC). Split-sample and direct-to-vial studies have shown that LBPs show an overall improvement in sample collection and processing, reduce artifacts that interfere in diagnosis, are more sensitive, can be utilized for ancillary tests and are a cost-effective replacement for CPS. Comparative analyses of diagnostic accuracy indicate that LBPs perform at least as well as CPS. However, the added advantages of standardized, automated preparations and screening, reduced unsatisfactory rate, improved specimen adequacy and ability to perform human papillomavirus (HPV) test, are enough to continue use of LBP. The cytologic features in LBP are similar to CPS with subtle differences, particularly in background information. There are also subtle differences between the two LBPs, SP and TP, which are reflective of different sampling devices, collection media, and processing techniques. Architecturally, LBP shows smaller cell clusters and sheets and more dyscohesion. Cytologically, enhanced nuclear features and smaller cell size are more prominent. Advances in liquid-based Papanicolaou's (Pap) test have lead to well-defined patient management guidelines by the American Society for Colposcopy and Cervical Pathology. Herein, we review these aspects of Pap test including, morphology, automation, ancillary tests (HPV and immunochemistry), pertinent QA/QC monitors, patient management guidelines, and review of pertinent literature.