Effects of the menstrual cycle on cytological false-negatives in women with persistent cervical intraepithelial neoplasia.

Abstract

False-negatives on cytology may be observed during follow-ups for patients with persistent cervical intraepithelial neoplasia (CIN); however, the underlying reasons are unknown, and the relationship between the intra-individual variability of false-negatives and the menstrual cycle phase has not been elucidated. Therefore, this study aimed to determine whether the menstrual cycle influences cytological results to maximise the accuracy of such tests. A total of 154 liquid-based cytological (LBC) samples were obtained during follow-ups for 26 patients with CIN, and the relationship between cytological results and the menstrual cycle, which was classified into six phases, was analysed. All LBC smears were satisfactory, and 20 of 154 (13.0%) specimens were negative for intraepithelial lesions or malignancy (NILM). A statistically significant association was observed between the cytological results and the phase of the menstrual cycle, χ2 (2)=19.322, P < 0.01. The association was moderately strong (Cramer's V=0.354). The value of adjusted residuals showed a statistically significant increase in the NILM percentage as a cytological result during the early secretory phase (P < 0.01) and a statistically significant decrease in NILM during the menstrual and proliferative phases (P < 0.01). The present study revealed that false-negative cytological results were found to more likely to occur during the early secretory phase. More careful and precise microscopic observation of Pap smears collected at the early secretory phase may contribute to a reduction in the occurrence of false-negatives and improve cytological sensitivity.