Detection of transformation zone cells in liquid-based cytology and its comparison with conventional smears.

BACKGROUND: To compare the differences between liquid-based cytology (LBC) and conventional cytology in respect of the detection of transformation zone cells (TZC) by age group and to assess test performance by correlating results with cytological abnormalities. METHODS: A retrospective study assessing the results of cervical-vaginal cytology smears collected at a private laboratory in São Paulo (Brazil) between January 2010 and December 2015. RESULTS: A total of 1 030 482 cytology tests were performed; of these, 3811 (0.36%) unsatisfactory samples were excluded. Cytology sampling in the patients studied was performed using the conventional technique in 394 879 (38.5%) cases and the liquid-based techniques in 631 792 (61.5%) cases. The proportion of samples with TZC for interpretation was 73.2% (288 956 samples) in conventional cytology and 52.7% (333 115 samples) in LBC (P < .001). The presence of TZC rate declined in both groups with age, but was consistently lower for LBC (P < .001). The presence of endocervical and metaplastic cells was associated with higher high-grade intraepithelial lesion detection rates. CONCLUSION: Low representation of the transformation zone was found in the samples collected using the LBC technique, particularly in the over 50 age group. Conventional cytology was associated with a higher rate of detection of high-grade lesions.