We thank Dr Jick for providing additional information about the criteria for patient selection in the cited studies. These important details were unfortunately omitted from the published methods. We agree that the fundamental principle is to apply the same exclusion criteria equally to both cases and control subjects. We did not assert that all persons with predictably high or low rates of exposure must be included in the study groups, but simply advised that such patients not be unequally excluded from either the case or control group. Equal exclusion of such patients from both groups is one acceptable alternative, but whether such equality was achieved in the cited studies remains uncertain. In the first study,1 for example, a woman with a recent diagnosis of breast cancer and chronic cardiovascular disease could be included in the case group, whereas a woman hospitalized for abdominal pain would be excluded
Hayden GF, Kramer MS, Horwitz RI. Case-Control Studies-Reply. JAMA. 1982;248(5):547. doi:10.1001/jama.1982.03330050030017
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