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 spontaneo us cervical screening practice in Ravenna, Italy. Negative/benign repo rts 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 im plemented. The aim of the present study was to evaluate the effects of such changes in the screening procedure. Methods: The frequency of UN S in 1990 was compared with that of UNS+RERS in 1988 (assumed as a bas eline year) by the calculation of the standardized rate ratio with the 95% confidence interval (CI). The trend in the standardized rate of U NS from 1990 to 1994 was evaluated by the calculation of the average a nnual variation with the 95% CI. Results: The immediate effect of TBS (1990:1988 comparison) was a significant increase in the rate of UNS a ttributable 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 t o 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 e ffect of TBS (trend from 1990 to 1994) was a decrease in the total rat e of UNS by an average of 2.3% per year. The downward trend was signif icant for smears showing scant cellularity, poor fixation and thick ar eas (-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 sub stantial change in the type of information provided by the cytology re port (immediate effect). The monitoring program according to TBS led t o a reduction in UNS attributable to sample taker (midterm effect).