Home-diagnosis of deep venous thrombosis with impedance plethysmography

In order to assess the value of I.P.G. for the diagnosis of D.V.T. in general practice, an I.P.G. was carried out by a skilled technician in 255 consecutive patients with suspected D.V.T. at home. Ascending venography was carried out in 185 of these patients. In addition, blood for assay of AT III, platelet count, fibrinogen, a2-antiplasmin, ethanol gelation test and spontaneous platelet aggregation was collected at the time the I.P.G. was performed. In 61 patients (33%) venography showed the presence of D.V.T., and was negative in the remaining 124 patients. I.P.G. was positive in 51 of the 61 patients with D.V.T., a sensitivity of 84%. I.P.G. was normal in 115 of the 124 patients with a negative venogram, a specificity of 93%. The sensitivity of the I.P.G. for proximal vein thrombosis was 92% and for calf vein thrombosis 68%. Mean a2-antiplasmin concentration was significant (p less than 0.05) lower (101 +/- 15%, mean +/- SD) in patients with D.V.T. compared with patients with a normal venogram (107 +/- 11%, mean +/- SD). No differences between the two groups were observed in the other coagulation parameters assayed, and none was of diagnostic value, either alone or in combination with I.P.G. This study shows that I.P.G. is of potential value for the home diagnosis of D.V.T., in particular proximal vein thrombosis. This is potentially clinically useful, because these thrombi are thought to carry a high risk for pulmonary embolism.