The dilute whole blood clot lysis assay: a screening method for identifying postoperative patients with a high incidence of deep venous thrombosis.

A dilute whole blood clot lysis assay was used to identify patients with a high incidence of DVT. Of 191 orthopedic and urologic patients who underwent surgery, the over-all incidence of DVT as determined by 125I-fibrinogen leg scan was 35% in the 92 individuals with abnormal assays and 1% in the 99 patients with normal assays. The likelihood that an individual patient might have developed DVT increased progressively with the number of abnormal assays (p less than 0.001). The incidence of DVT increased from 28% in patients who had one abnormal assay, to 35% in patients with two abnormal assays, to 56% in patients with three abnormal assays. These studies establish the clot lysis assay as a simple means to screen for patients with a high incidence of DVT. A normal assay can eliminate patients from consideration for more extensive studies (venography, fibrinogen scan, impedance plethysmography), whereas those patients with one or more abnormal assays should be seriously considered for these additional studies.