RT Journal
A1 Lehman RG
T1 DIcumarol dosage adjusted to prothrombin activity
JF Journal of the American Medical Association
JO Journal of the American Medical Association
YR 1955
FD October 29
VO 159
IS 9
SP 969
OP 969
DO 10.1001/jama.1955.02960260139018
UL http://dx.doi.org/10.1001/jama.1955.02960260139018
AB To the Editor:— 
    The intelligent use of anticoagulant agents is currently restricted because determinations of prothrombin activity must be accurate and many laboratories continue to have difficulty with such determinations. Where the method used employs a standard wherein 100% activity is a relatively short time in seconds (such as 13-15 seconds), a minute difference in seconds in the result of the patient's prothrombin activity is capable of producing a serious error in anticoagulant dosage and resultant difficulty for the physician.The San Pedro Community Hospital has for a few years used the Owren-Ware method (Ware, A. G., and Stragnell, R.: An Improved One-Stage Prothrombin Method, Am. J. Clin. Path.22:791 [Aug.] 1952) of determining prothrombin activity. This method utilizes a 100% standard that usually is 20-25 seconds. With this method, 20% activity is two to two and one-half times the control in seconds, so that prothrombin activity under anticoagulant