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April 17, 1972

Oral Contraceptives and Thromboembolic Disease

Author Affiliations

The Johns Hopkins University School of Hygiene & Public Health Baltimore

JAMA. 1972;220(3):416. doi:10.1001/jama.1972.03200030074024

To the Editor.—  Dr. Drill's paper on oral contraceptives and thromboembolic disease (219:583, 1972) makes some erroneous statements about a study by my colleagues and myself1 which should be corrected. He states that an increased hospital admission risk was found for certain cities but not for others, and for certain diagnoses but not for others.In all five cities in our study, the use of oral contraceptives was associated with thromboembolism. In the two areas with the smallest numbers of cases the association was not statistically significant. Using R. A. Fisher's method for the combination of probabilities from tests of signigicance, it can be shown that the overall association is highly significant (P <.001). Likewise, for each of the five thromboembolic conditions encountered often enough to permit a significance test to be conducted, there was association with the use of oral contraceptives, which reached a level of significance for