Effects of the Bethesda System on the rate of unsatisfactory Pap smears in spontaneous cervical screening.

AIMS: In 1990, The Bethesda System (TBS) was introduced into spontaneous cervical screening practice in Ravenna, Italy. Negative/benign reports with the recommendation for early repeat smears (RERS) due to some limitation in sample adequacy were considered no longer acceptable. A monitoring program for the rate of unsatisfactory smears (UNS) was implemented. The aim of the present study was to evaluate the effects of such changes in the screening procedure. METHODS: The frequency of UNS in 1990 was compared with that of UNS+RERS in 1988 (assumed as a baseline year) by the calculation of the standardized rate ratio with the 95% confidence interval (CI). The trend in the standardized rate of UNS from 1990 to 1994 was evaluated by the calculation of the average annual variation with the 95% CI. RESULTS: The immediate effect of TBS (1990; 1988 comparison) was a significant increase in the rate of UNS attributable to scant cellularity, poor fixation and thick areas (rate ratio, 2.35; 95% CI, 2.18 to 2.53) and to the absence of endocervical component (1.45; 95% CI, 1.30 to 1.60). The rate of UNS attributable to the presence of cytolysis, inflammation, blood and foreign material decreased by about 6 times (0.16; 95% CI, 0.13 to 0.19). The midterm effect of TBS (trend from 1990 to 1994) was a decrease in the total rate of UNS by an average of 2.3% per year. The downward trend was significant for smears showing scant cellularity, poor fixation and thick areas (-1.5% per year) and the absence of endocervical component (-0.7% per year). UNS attributable to the presence of cytolysis, inflammation, blood and foreign material stabilized. CONCLUSIONS: TBS led to a substantial change in the type of information provided by the cytology report (immediate effect). The monitoring program according to TBS led to a reduction in UNS attributable to sample taker (midterm effect).