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To the Editor:
—The letter of Dr. Iversen and associates does not invalidate the fundamental criticism that their treated and untreated cases were not chosen by random selection (alternate case method). This method requires unswerving assignment of successive patients alternately to the treated and untreated groups. Neither the original report from Copenhagen nor the above letter claims to have followed this procedure of random selection. Distribution of patients through a central office, which was unaware of the study, does not denote such selection. Alternate case distribution was impossible unless the central office knew of the study.It is difficult to understand how, over a period of 4 yr, hospital professional staff, other personnel, the patients themselves, and eventually their physicians should not be aware that patients in two departments of two hospitals were not receiving the well-known anticoagulant treatment while such treatment was being administered in the other two departments
Friedberg CK. Anticoagulant Therapy in Acute Myocardial Infarction. JAMA. 1963;183(10):904. doi:10.1001/jama.1963.03700100129037
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