[Evaluation of mass screening for cervical cancer in Shiga Prefecture].

During 1969 and 1979 cervical cancer was found in 269 women out of a population of 166,202 who were attending mass screening for cervical cancer in Shiga Prefecture, Japan. The overall 0.162% detection rate for this disease in the mass screening was within the range reported from other prefectures in Japan. The peak prevalence of carcinoma in situ was found at ages 40 to 44 years, while invasive cancer was found evenly distributed between ages 35 and 54 years. Among 269 women with cervical cancer, 68.8% were found to have suspicious or positive smears at the time of the initial screening, and 94% were detected by the time of the third screening. Ten women with carcinoma in situ had received the screenings almost annually more than three times and were found to have suspicious or positive smears at the time of the fourth or fifth screening. Re-evaluation of previous smears in these patients revealed that 55.6% should have been diagnosed as positive smears. Also eight women with cervical cancer in stage Ia or Ib were initially found to have positive smears at the time of the second screening, and re-evaluation of their previous smears showed that 50% had been suspicious or positive smears at the initial screening. These findings indicate that annual repeat screenings for at least three years are necessary for the early detection of cervical cancer. It is also emphasized that laboratory quality and/or accuracy should be properly controlled to avoid false negative results.