Thromboembolic disease:: Variability of interobserver agreement in the interpretation of CT venography with CT pulmonary angiography

OBJECTIVE, The objective of this study was to determine interobserver agreement in the diagnosis of acute deep venous thrombosis on CT venography performed in addition to CT pulmonary angiography. SUBJECTS AND METHODS. One hundred forty-six CT venograms of 144 patients (mean age, 61.74 years) clinically suspected of having pulmonary embolism were analyzed prospectively and independently by two experienced thoracic and body imaging radiologists and later by consensus of the two radiologists. The CT venography protocol consisted of 5-mm-thick axial images at 20-mm intervals from the popliteal fossa to the renal veins. Images were acquired 3-4 min after the start of 100-150 ml of undiluted contrast medium administration at 4 mL/sec. Thirteen venous segments were analyzed in each patient, There were 1586 analyzable venous segments. RESULTS, Interobserver agreement, with the patient as the unit of analysis, was moderately good (kappa, 0.59; 95% confidence interval [CI], 0.39-0.78). Kappa values were similar for CT venography studies performed with 150 mL of contrast medium and 4-min delay (kappa, 0.62; 95% CI, 0.30-0.88) and with 3-min delay and 100 mi of contrast medium (kappa, 0.56; 95% CI, 0.32-0.80). Interobserver disagreement occurred in 17 (12%) of 146 CT venography studies. Findings of 11 CT venography studies were interpreted as negative, and six were interpreted as positive after consensus interpretation. CONCLUSION. Interobserver agreement for deep venous thrombosis with CT venography is moderately good.