Bedside Testing (SimpliRED) in the Diagnosis of Deep Vein Thrombosis

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Abstract
The authors evaluate the sensitivity and specificity of a bedside test (SimpliRED) in the diagnosis of deep vein thrombosis compared with contrast phlebography. Two hundred fifty patients, referred for phlebography, underwent bedside testing for detection of deep vein thrombosis. Contrast phlebography was performed immediately afterward. SimpliRED provides a clearly visible agglutination of the patient's red blood cells in the presence of elevated levels of cross-linked fibrin derivative (D-dimer), which is specific for fibrin breakdown. In 82 (32.8%) patients, deep vein thrombosis was confirmed venographically. An abnormal D-Dimer test was found in 79 of the 82 patients with thrombosis (sensitivity: 96.3%). The three patients who were diagnosed falsely as normal on agglutinin testing, had venograms which showed only an isolated calf thrombosis in small muscle veins (< 2 cm in diameter) not requiring treatment. One hundred of 168 patients without venographic thrombosis were diagnosed correctly by SimpliRED (specificity: 59.5%). The positive predictive value was 53.7%; the negative predictive value was 96.8%. All thrombotic disorders in the leg that required further treatment were identified correctly. SimpliRED is a very sensitive test with moderate specificity in the diagnosis of deep vein thrombosis. Therefore, further invasive testing is needed only in those patients in whom the D-dimer test is abnormal. A false-positive result of the bedside test may be nonspecific or due to elevated levels of fibrin split products, which can occur whenever the coagulation system has been activated by any of several conditions.