Influence of Variability of Interpretation of Contrast Venography for Screening of Postoperative Deep Venous Thrombosis on the Results of a Thromboprophylactic Study

Summary

To assess interobserver variability of venography for screening for postoperative deep venous thrombosis (DVT), we used 185 bilateral ascending contrast venograms (366 lower limbs) which were performed using the 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 readers 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 evaluation: 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 from 89 to 93% (Kappa 0.63-0.74) for the comparison between the readers and the initial evaluation. This considerable degree of disagreement among experienced readers should be taken into account in calculating sample 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 other one depending upon the reading of venograms.

• References

• 1 Büller HR, Lensing AWA, Hirsh J, ten Cate JW. Deep vein thrombosis: new non-invasive diagnostic tests. Thromb Haemostas 1991; 66: 133-137
• 2 Naidich JB, Feinberg AW, Karp-Harman H, Karmel MI, Tyma CG, Stein HL. Contrast venography: reassessment of its role. Radiology 1988; 168: 97-100
• 3 Lensing AWA, Büller HR, Prandoni P. et al. Contrast venography, the gold Standard for the diagnosis of deep-vein thrombosis: improvement in observer agreement. Thromb Haemostas 1992; 67: 8-12
• 4 Redman HC. Deep venous thrombosis: is contrast venography still the diagnostic “gold Standard”?. Radiology 1988; 168: 277-278
• 5 Mattos MA, Londrey GL, Leutz DW. et al. Color-flow duplex scanning for the surveillance and diagnosis of acute deep venous thrombosis. J Vase Surg 1992; 15: 366-376
• 6 Kakkar VV. Fibrinogen uptake test for detection of deep vein thrombosis. A review of current practice. Semin Nucl Med 1977; 7: 229-244
• 7 Lensing AWA, Hirsh J. ¹²⁵I Fibrinogen leg scanning: Reassessment of its role for the diagnosis of venous thrombosis in post-operative patients. Thromb Haemostas 1993; 69: 2-7
• 8 McLachlan MSF, Thomson JG, Taylor DW, Kelly ME, Sackett DL. Observer Variation in the interpretation of lower limb venograms. AJR 1979; 132: 227-229
• 9 Illescas FF, Ledere J, Rosenthall L. et al. Interobserver variability in the interpretation of contrast venography, ^99mTechnetium red blood cells venography and impedance plethysmography for deep vein thrombosis. J Can Assoc Radiol 1990; 41: 264-269
• 10 Lea Thomas M, Chan TYK, Wong WL. The phlebographic diagnosis of deep vein thrombosis - a study in observer Variation. Phlebology 1991; 6: 99-102
• 11 Wille-Jorgensen P, Borris L, Jorgensen LN. et al. Phlebography as the gold Standard in thromboprophylactic studies? A multicenter interobserver variaton study. Acta Radiol 1992; 33: 24-8
• 12 Bounameaux H, Prins TR, Schmitt HE, Schneider PA. Venography of the lower limbs: pitfalls of the gold Standard. Invest Radiol 1992; 27: 1009-1011
• 13 Rabinov K, Paulin S. Roentgen diagnosis of venous thrombosis in the leg. Arch Surg 1972; 104: 134-144
• 14 Bounameaux H, Huber O, Khabiri E, Schneider PA, Didier D, Rohner A. Unexpectedly high rate of phlebographic deep venous thrombosis following elective general abdominal surgery among patients given prophylaxis with low-molecular-weight heparin. Arch Surg 1993; 128: 326-328
• 15 Cohen J. A coefficient of agreement for nominal scales. Educ Psych Meas 1960; 20: 37-46
• 16 Cohen J. Weighted kappa: nominal scale agreement with provision for scaled disagreement or partial credit. Psychol Bull 1968; 70: 213-220
• 17 Salzman EW. Venous thrombosis made easy. N Engl J Med 1986; 314: 847-848
• 18 Borris LC, Christiansen HM, Lassen MR. et al. Comparison of real-time B-mode ultrasonography and bilateral ascending phlebography for detection of postoperative deep vein thrombosis following elective hip surgery. Thromb Haemostas 1989; 61: 363-365
• 19 Leyvraz PF, Bachmann F, Hoeck J. et al. Prevention of deep vein thrombosis after hip replacement: randomised comparison between unfractionated heparin and low molecular weight heparin. Br Med J 1991; 303: 543-548