Background: It is commonly believed that the sensitivity of Papanicolaou (Pap) tests decreases with a short interval between cytology samplings. To the authors' knowledge, there is only limited evidence to support this belief.
Methods: For 5055 women in the Atypical Squamous Cells of Undetermined Significance (ASCUS)-Low Grade Squamous Intraepithelial Lesion (LSIL) Triage Study (ALTS), the Pap interval was defined as the number of days between the referral Pap smear demonstrating ASCUS or LSIL ("first cytology") and the enrollment liquid-based ("repeat") cytology. The authors investigated the influence of the interval between Pap smears on repeat cytology by examining percentages of abnormal findings, cellularity, and test sensitivity among women diagnosed with histologic grade 3 cervical intraepithelial neoplasia (CIN3) during the 2-year course of the ALTS. In addition, because human papillomavirus (HPV) DNA adjunct testing is now performed, the authors evaluated HPV viral load, which was assayed using residual liquid cytology specimens, in women with CIN3.
Results: The Pap interval ranged from 8-30 days in 763 women, 31-60 days in 2317 women, 61-90 days in 1090 women, 91-120 days in 491 women, and 121-184 days in 394 women (mean of 61.3 days; standard deviation of 34 days). Repeat cytologic interpretations of unsatisfactory findings, ASCUS, and high-grade squamous intraepithelial lesion (HSIL) did not appear to vary among the Pap interval groups. However, low-grade cytologic regression occurred with an increasing Pap interval; negative cytology increased from 28.3% (8-30 days) to 41.6% (121-184 days) (P < 0.0001) whereas LSIL cytology decreased (P trend = 0.002). The approximate cellularity of the samples was slightly better in the interval group of 8-30 days (P trend = 0.04). Among women with CIN3, the repeat test sensitivity at a threshold of ASCUS or greater and the HPV DNA viral load was not found to vary by Pap interval (P trend = 0.80 and P trend = 0.36, respectively).
Conclusions: The authors concluded that a short Pap interval (range, 15-120 days) does not significantly affect the quality of liquid-based repeat cytology, nor the viral load tested from a residual liquid-based specimen.