[Duplex ultrasonography in the diagnosis of deep vein thrombosis of the legs. Agreement between two operators].
The operator-dependent nature of venous Duplex-ultrasonography diagnosis of deep venous thrombosis (DVT) of the leg is the principal reproach applied to it and a reason for delaying use. The aim of the present study was to evaluate concordance between two operators, with rigorous application of the same methodology of exploration of the venous axes. The study included 82 patients under hospital care, randomly selected from among those referred for the first Duplex-ultrasonography examination for DVT, and having accepted to undergo 2 consecutive explorations, one by each of the two operators. The two operators evaluated independently, for the 19 venous axes of the legs: 1: the interpretability of the examination, 2: the differential diagnosis between: absence of thrombus, presence of thrombus, nonconclusive examination, and 3: the score for the DVT extension. Evaluation of concordance of diagnosis was by Cohen's kappa coefficient, calculated on the positive diagnosis of DVT and the site of the most proximal thrombus. Extension scores were compared by calculation of the coefficient of correlation "r". Interpretability rates were 92% and 91% respectively for the two operators, 35 DVT being diagnosed in 27 patients by operator A and 36 DVT in 27 patients by operator B. The kappa coefficient for diagnosis of DVT with localization in the affected leg was 0.90 [0.81-0.98]. It was 0.89 [0.73-1] for proximal lesions, 0.86 [0.74-0.97] for the lower leg level, and 0.79 for localization of the proximal extremity of the thrombus. Extension scores evaluated by the two operators were 2.88 and 3.14 respectively, with a coefficient of correlation between the extension scores of 0.96. The 5 diagnostic divergences concerned the lower leg level; the 2 localization discordances concerned: the frontier zones leg-lower popliteal, lower femoral-upper popliteal. Good concordance between results of the two operators using Duplex-ultrasonography exploration was obtained even though the majority of the DVT were in the calf, a region known to be explored with difficulty. Overcoming the operator-dependent character of Duplex-ultrasonography by a rigorous exploratory methodology could make it the future reference examination for the diagnosis of DVT.