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July 28, 1978

Antithrombin III Assays

Author Affiliations

Loyola University Medical Center Maywood, III

JAMA. 1978;240(4):345-346. doi:10.1001/jama.1978.03290040023006

To the Editor.—  In a recent letter to the editor, Rodger L. Bick, MD, commented on methods of assay of antithrombin III (239:296, 1978), pointing out several drawbacks to the use of synthetic chromogenic substrates in such assays. His comments were prompted by an article in MEDICAL NEWS (238:1005, 1977) in which we reported that these peptides were useful in the assay of antithrombin III, emphasizing, however, that they were as yet experimental.Since we believe that these methods are useful in the assay of antithrombin III, we have looked at the studies to which Dr Bick referred and find problems that have been successfully circumvented in these assays.The study by Gaffney and his associates1 showing deterioration of stored frozen thrombin is not strictly pertinent to antithrombin III assays by these methods since thrombin was shown to lose its clotting activity but not its amidolytic activity.Autolytic forms