The letter from Drs Pastakia and MacKinney is well taken. Certainly, we would welcome any new alternatives to fibrinogen I 125 scanning as a screening procedure for the detection of deep venous thrombosis. I hope, however, that these new radioisotopes would be subjected to the same trials reported in our article, to determine whether or not they are, indeed, offering a more accurate screening test.
I believe some of the difficulties clinicians have had with fibrinogen I 125 leg scanning are attributable to the fact that a radioisotope is being used; some clinicians compare it to pulmonary scintillation scanning. I think there is general agreement that if pulmonary scintillation scanning results are negative, the possibility of embolization is virtually nil. The unconscious transfer of this concept to leg scanning is very dangerous because the sensitivity of leg scanning is so low that one may be lulled into a false