A reanalysis of the Cu-7 intrauterine contraceptive device clinical trial and the incidence of pelvic inflammatory disease: A paradigm for assessing intrauterine contraceptive device safety

OBJECTIVE: We calculated and compared the incidence of pelvic inflammatory disease in a 10% random sample of the Cu-7 intrauterine contraceptive device (G.D. Searle & Co., Skokie, Ill.) clinical trial with the rates reported to the Food and Drug Administration and those in subsequent trials published in the world literature. STUDY DESIGN: A 10% random sample of the Cu-7 clinical trial was examined because calculations had demonstrated this random sample to be sufficient in size (n = 1614) to detect a difference in rates of pelvic inflammatory disease from those reported to the Food and Drug Administration. An audit of a subset of the patient files, compared with the original files in Skokie, Illinois, confirmed that the files available for analysis were complete. Standard definitions were used to identify cases of pelvic inflammatory disease and to calculate rates of pelvic inflammatory disease. The world literature on Cu-7 clinical trials was reviewed. RESULTS: The calculated crude and Pearl index rates of pelvic inflammatory disease were consistent with those rates previously reported to the Food and Drug Administration and published in the medical literature. Life-table pelvic inflammatory disease rates were not different between nulliparous and parous women and pelvic inflammatory disease did not differ from basal annual rates in fecund women. CONCLUSION: On the basis of the analysis of this 10% sample, the pelvic inflammatory disease patient rates reported to the Food and Drug Administration for the entire Cu-7 clinical trial are accurate and are similar to those published in the world literature. (AM J Obstet Gynecol 1994;170:1606-16.)