To the Editor.
—I would like to comment on the article entitled "The Limited Utility of Fibrinogen I 125 Leg Scanning" in the February issue of the Archives (139:148-153, 1979).The sine qua non of a deep venous thrombosis according to this investigation is the venogram. Since it assumes that a normal venogram rules out the presence of a clot, any other study that indicates that there is a clot is automatically designated as a falsepositive. Since specificity is a truenegative divided by the sum of a true-negative and a false-positive, specificity is based on a study that may in fact be in error. In the absence of any false-positives, specificity as indicated here would be 100%.Sensitivity is designated as a truepositive divided by the sum of a truepositive and a false-negative, again based on the assumption that a venogram is the standard. In the absence of any false-negatives,