The fallibility of the clinical diagnosis of
deep venous thrombosis (DVT) and
postphlebitic syndrome has led to a variety of noninvasive diagnostic modalities, e.g, Doppler ultrasound, plethysmography, and
radionuclide phlebography. The purpose of this study is to analyze the value of combined strain gauge plethysmography (SPG) and I-125
fibrinogen leg scanning in the differentiation of DVT and
postphlebitic syndrome. Using strain gauge plethysmograph, 600 studies were performed on 502 patients. The maximum venous outflow (MVO) was calculated. An MVO of 20 cm3/100 cm3 of tissue/min or above was considered normal, and MVO of less than 20 cm3 was abnormal. Of those, 150 limbs had I-125
fibrinogen leg scan and venograms. Of 82 normal SPG, when compared with venograms, 75 were normal, five had
postphlebitic syndrome, and two had DVT (97.6% true-negative). Sixty-eight legs had positive SPG, 46 of which had DVT (67.6% true-positive), 21 had
postphlebitic syndrome (30.9%), and one was normal (1.5% false-positive). When rubber
tourniquets were placed lightly on each leg between the strain gauge and the thigh cuff, 12 legs changed from positive SPG to negative SPG; 56 legs only had positive SPG. Forty-six of these had DVT (82.1% true-positive), nine had
postphlebitic syndrome, and one was normal. When positive SPG was combined with positive leg scan, the accuracy raised to 95.6% (44 of 46 legs). If the SPG was positive but the leg scan was negative, the possibility of
postphlebitic syndrome was most likely (8 of 10, i.e., 80%).