INFLUENCE OF VARIABILITY OF INTERPRETATION OF CONTRAST VENOGRAPHY FORSCREENING OF POSTOPERATIVE DEEP VENOUS THROMBOSIS ON THE RESULTS OF ATHROMBOPROPHYLACTIC STUDY

To assess interobserver variability of venography for screening for po stoperative deep venous thrombosis (DVT), we used 185 bilateral ascend ing contrast venograms (366 lower limbs) which were performed using th e long-leg film technique, in the frame of a trial of the efficacy of two low-molecular-weight-heparin fractions (initial evaluation). These venograms were submitted in a multicenter setting to three further re aders who performed a serial scoring as DVT, no DVT or non-evaluable. DVTs were diagnosed in 78, 55 and 59/366 limbs (initial evaluation: 58 ). The proximal locations of DVTs were 16, 9 and 16 (initial evaluatio n: 15) and the non evaluable limbs 3, 5 and 18 (initial evaluation: 0) . Apparent pairwise agreement between the three readers ranged from 87 to 90% (true coefficient of agreement Kappa 0.63-0.70). It ranged fro m 89 to 93% (Kappa 0.63-0.74) for the comparison between the readers a nd the initial evaluation. This considerable degree of disagreement am ong experienced readers should be taken into account in calculating sa mple sizes in prospective thromboprophylactic studies. Indeed, one of the two prophylactic regimens proved to be significantly (p = 0.012, p = 0.031, p = 0.049 or non-significantly (p = 0.073) superior to the o ther one depending upon the reading of venograms.