Context: The cytomorphology of liquid-based preparations in urine cytology is different than classic slide preparations.
Objectives: To compare the performance of liquid-based preparation specimens to classically prepared urine specimens with a malignant diagnosis in the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytology.
Design: Participant responses between 2000 and 2007 for urine specimens with a reference diagnosis of high-grade urothelial carcinoma/carcinoma in situ/dysplasia (HGUCA), squamous cell carcinoma, or adenocarcinoma were evaluated. ThinPrep and SurePath challenges were compared with classic preparations (smears, cytospins) for discordant responses.
Results: There were 18 288 pathologist, 11 957 cytotechnologist, and 8086 "laboratory" responses available. Classic preparations comprised 90% (n = 34 551) of urine challenges; 9% (n = 3295) were ThinPrep and 1% (n = 485) were SurePath. Concordance to the general category of "positive-malignant" was seen in 92% of classic preparations, 96.5% of ThinPrep, and 94.6% of SurePath challenges (P < .001). These results were statistically different for the exact reference interpretation of HGUCA (P < .001) but not for adenocarcinoma (P = .22). Cytotechnologists demonstrate statistically better performance for the general category of "positive-malignant" compared with pathologists for all urinary slide types and for the exact reference interpretation of HGUCA (94% versus 91.1%; P < .001) but not adenocarcinoma (96.3% versus 95.8%; P = .77) or squamous cell carcinoma (93.6% versus 87.7%; P = .07).
Conclusions: Liquid-based preparations performed significantly better in urinary cytology challenges when evaluating malignant categories in the College of American Pathologists interlaboratory comparison program. The liquid-based preparation challenges also performed better for the exact reference interpretation of HGUCA, but no difference was observed for adenocarcinoma challenges. Cytotechnologists perform better than pathologists for all slide types, as well as those demonstrating HGUCA. These results suggest that liquid-based preparations facilitate a more accurate diagnosis than conventional preparations.