Does Menstruation Affect Pap Test Accuracy?
For conventional cytology Pap tests, menstruation should prompt postponement of the test, while liquid-based cytology can be performed at any time during the menstrual cycle. 1
Type of Pap Test Determines Timing
Conventional Cytology (Slide-Based)
- Should be postponed if a woman is menstruating 1
- The woman should be advised to have a Pap test at the earliest opportunity after menses 1
- Ideally should be scheduled for 10-20 days after the first day of menses 1
- During the first four days of the menstrual cycle, approximately 20% of conventional smears are of insufficient quality for cytologic diagnosis 2
Liquid-Based Cytology
- Can be performed at any time during the menstrual cycle 1
- This represents a significant practical advantage over conventional cytology 1
- Liquid-based cytology produces fewer inadequate readings and false-negative results compared to conventional methods 1
Evidence on Menstrual Cycle Phase Effects
The relationship between menstrual cycle phase and Pap test accuracy shows conflicting evidence:
Studies Suggesting Cycle Effects
- One study found false-negative cytological results were more likely during the early secretory phase in women with persistent cervical intraepithelial neoplasia (CIN), with a statistically significant association between cytological results and menstrual cycle phase 3
- This study suggested more careful microscopic observation of Pap smears collected during the early secretory phase may reduce false-negatives 3
Studies Showing No Significant Difference
- A community-based study using colposcopy as the gold standard found no significant difference in sensitivity, specificity, positive predictive value, negative predictive value, or accuracy of Pap smears performed during proliferative versus secretory phases 4
- This study concluded that Pap smears can be collected during either phase of a woman's menstrual cycle 4
Practical Clinical Approach
Schedule conventional cytology Pap tests when the patient is not actively menstruating, ideally 10-20 days after the first day of menses. 1
If using liquid-based cytology, schedule at the patient's convenience without regard to menstrual cycle timing. 1
Important Caveats
- The presence of mucopurulent discharge should not delay the Pap test—the test can be performed after careful removal of the discharge with a saline-soaked cotton swab 1
- Recent sexual intercourse does not require postponement of Pap testing, as the sequence of Pap testing in relation to collection of other cervicovaginal specimens has not been shown to influence results or interpretation 5
- Women using oral hormonal contraceptives have an increased risk for unreliable quality smears, with higher quality smears obtained during the first half of the cycle 2