Use of flow cytometry as a quality control device for liquid-based cervical cytology specimens

Cervical cancer is the second most common cancer in women worldwide comprising a major concern of public health. Liquid-based cytology provides significantly more effective detection of low-grade intraepithelial neoplasia or more severe lesions, without loss of diagnostic specificity and reduces the number of cases classified as unsatisfactory. The objective of the study is the evaluation of flow cytometry as a rapid tool for quality control of the liquid specimen adequacy for the purpose of precise cytological diagnosis in detecting cervical abnormalities.

A total of 1,854 women undergoing routine cervical cytology joined this cohort study. A monolayer smear was prepared and 1 ml aliquot was removed and prepared for flow cytometric analysis. Cells were fixed and run on a Partec CyFlow SL, with front scatter (FSS) and side scatter (SSC) set on logarithmic scale. The forward scatter versus side scatter dot-plot was used for the distinction of ectocervical, endocervical, and polymorphonuclear cells.

In the total of 1,854 cases, 15 specimens (0.8%) were characterized by the cytopathologist as unsatisfactory. Inadequacy was confirmed by flow cytometric analysis for four samples. Monolayer smears were reprepared for the remaining 11 samples. After the second microscopic observation, six out of the 11 cases (54.5%) were found to be satisfactory, whereas the remaining five were still designated as unsatisfactory by the cytopathologist.

The parallel screening of adequacy by quantification of cell populations with flow cytometry can serve as an internal control for diagnosis and can overall decrease the number of unsatisfactory samples.