A CASE CONTROL STUDY TO ESTIMATE THE DETECTION OF CANCER OF THE CERVIX UTERI BY CYTOLOGY

  • 1 January 1984
    • journal article
    • research article
    • Vol. 32  (1) , 10-15
Abstract
A case control study was carried out in Geneva, Switzerland to verify the efficacy of early detection of cancers of the cervix uteri by cytology and to estimate the degree of protection. The study included the 186 incident cases of invasive cancer occurring in the time period 1970-76 and also fulfilling the condition of having lived at least 10 yr in Geneva. Each case is matched to 1 control according to age, nationality (Swiss/foreigners), civil state (unmarried/other). The control had also to be a resident for 10 yr. The analysis was based on the number of negative smears during the observation period; this period commenced 10 yr before the date of incidence but not earlier than Jan. 1, 1964. The observation period ended when there was a positive smear or when there was an interval of less than 6 mo. between 2 negative smears. Each observation period is the same for both case and control. The protection conferred is significant and is estimated to be 3.2 (1.8-5.9) for women having had at least 1 negative smear. On the other hand, the degree of protection tends to diminish in direct proportion to the number of negative smears. This paradoxical result may be attributed to a selection effect of symptomatic cases among women undergoing repeated cytological examinations.

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