Short interval between two Pap smears: effect on the result of the second smear? A prospective randomized trial.

PURPOSE: A repeat Pap smear is sometimes necessary after a short time interval or even immediately, when patients seek for a second opinion or due to study participation. Only limited information is available on the possible impact of a short interval between two Pap smears. Most institutions therefore practice a minimum time span of 6-8 weeks before obtaining a second smear since a short interval is commonly believed to be associated with an increase of false negative results in the second smear.

METHODS: Two consecutive Pap smears were obtained from 81 women. 41 smears were processed using the conventional technique, whereas liquid-based cytology was used in the remaining 40 women. Smears were independently evaluated by four different cytopathologists. We analyzed the effect of time interval, both processing techniques and inter-observer variance in cytological evaluation.

RESULTS: While the result of the second smear shows a tendency towards a more benign outcome (odds ratio (OR) 1.436, 95% CI 0.972-2.121), this difference was not statistically significant (p = 0.07). No significant differences were observed between conservative and liquid-based cytology (OR 1.554, 95% CI 0.659-3.667, p = 0.31). There was considerable inter-observer variability, and the observer was a strong predictor of the cytological result (OR 0.632-5.083, 95% CI 0.355-8.975, p < 0.01).

CONCLUSIONS: We document a tendency towards a more benign outcome without statistical significance in the second smear. Inter-observer variability of different cytopathologists is high and should be kept in mind when evaluating cytology results.