DAVID PRAGER, M.D.
To the editor: The recent perspective by I. S. Wright, M.D., (1) has prompted this communication. I am surprised that Dr. Wright has emphasized the laboratory control of the Coumadin® drugs utilizing percent activity of normal instead of seconds as the unit of measurement of the Quick test. To explain further, I will describe how the value of percent activity of normal is obtained. Pooled, normal plasma that is assumed to be 100% of normal activity is diluted with any variety of diluents (barium-sulfate-adsorbed human plasma, barium-sulfate-adsorbed beef plasma, 0.85% saline, imidiazole-saline buffer). An aliquot of the pooled plasma is
PRAGER D. Prothrombin Time: Percent vs Seconds. Ann Intern Med. ;72:287. doi: 10.7326/0003-4819-72-2-287
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Published: Ann Intern Med. 1970;72(2):287.
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