In-111 platelet scintigraphy for detection of lower-extremity deep venous thrombophlebitis: Are 4-hour delayed images sufficient

Twenty-one nonheparinized patients suspected of having lower-extremity deep venous thrombosis underwent 4- and 24-hour In-111-labeled platelet scintigraphy (PS) and lower-extremity contrast venography (CV). Eleven of the 21 patients (52%) had one or more intraluminal filling defects on CV, indicating active thrombophlebitis. In seven of these 11 patients (64%) In-PS was abnormal at 4 hours, and in ten (91%) at 24 hours. All patients with abnormal studies at 4 hours showed greater uptake of more abnormal sites at 24 hours. Of the ten patients with CV-negative studies, two had abnormal bilateral lower pelvis/upper thigh uptake in In-PS at 24 hours. These two In-PS studies were considered to be false positive. Twenty-four-hour In-PS images are necessary if 4-hour images show faint focal uptake of asymmetric blood pool activity, or are normal