Excessive blood may compromise gynecologic Papanicolaou (Pap) smears. Liquid-based cytologic techniques have been developed in part to address this problem. In the current study, conditions of excessive blood were simulated to compare the ability of two liquid-based systems, ThinPrep and SurePath, to satisfactorily process specimens in the presence of this potentially limiting factor.
Equal volumes of washed epithelial cells derived from pooled residues of liquid Pap vials were added to a series of ThinPrep and SurePath vials. Increasing volumes of freshly drawn, packed erythrocytes were added to the vials in progressive amounts from 50 microL or 100 microL up to 3000 microL. The vials were processed on their respective instruments according to U.S. Food and Drug Administration-approved procedures for a total of six test runs. The cellularity of the slides was measured by averaging epithelial cell counts in a total of five 40x fields.
SurePath preparations were uncompromised by blood until aliquots from 1000 microL to 3000 microL were reached. The ThinPrep system invariably was overwhelmed by the first 50-microL or 100-microL aliquot of blood, with epithelial cell counts dropping immediately to near zero.
The cell enrichment process of the SurePath system capably handled significantly greater amounts of potentially obscuring blood than the membrane filtration method of the ThinPrep system, which was compromised by as little as

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