Validation of the Caprini risk assessment model for venous thromboembolism in high-risk surgical patients in the background of standard prophylaxis

Abstract

We used the Caprini venous thromboembolism risk assessment score to prospectively evaluate if there was a correlation between the Caprini scores and the incidence of postoperative deep vein thrombosis (DVT) in high-risk surgical patients. A second objective was to determine whether patients at extremely high risk need a more effective prophylactic regimen. This prospective multicenter observational study involved 140 high-risk patients who underwent abdominal (48%) or cranial and/or spinal (52%) surgery. All patients were assessed using the Caprini model and had a mean score of 9.5 ± 2.7 (range, 5-15). Our standard prophylaxis for venous thromboembolism consisted of above-knee graduated compression stockings with 18 to 21 mm Hg pressure and subcutaneous low-dose unfractionated heparin three times per day, starting on the first or second through the fifth postoperative day depending on the risk of bleeding. We performed a duplex ultrasound examination at baseline during the first 12 to 24 hours after surgery and then every 3 to 5 days until discharge to assess the lower limb venous system up to the inferior vena cava. The end point of the study was ultrasound verification of fresh DVT or pulmonary embolism (PE). Verification of PE was made in all cases of DVT using echocardiography, lung scintigraphy, combined single-photon emission computed tomography and X-ray computed tomography, or autopsy. Fresh postoperative DVT was found in 39 patients (28%). The incidence of DVT was 2% in patients with a Caprini score of 5 to 8, 26% in patients with scores of 9 to 11, and 65% in patients with scores of 12 to 15 (P for trend < .01). The risk for DVT was increased 18.7-fold for patients with scores of 9 to 11 and 98.4-fold for scores of 12 to 15 compared with patients with scores of 5 to 8. The area under the receiver operating characteristic curve was 0.87 (95% confidence interval, 0.81-0.94) and a Caprini score of 11 was the cutoff point that provided the highest sensitivity combined with highest specificity. In the 77 patients with a score of <11, DVT occurred in 2 patients (3%). In contrast, in the 63 patients with a score of ≥ 11, DVT occurred in 37 patients (59%; P < .01). PE was found in 13 patients (9%) and confirmed with autopsy. In all cases, verified fresh DVT was the source of embolism. There was a significant correlation between Caprini scores and the incidence of postoperative DVT in high-risk surgical patients. A Caprini score of ≥ 11 can identify a subgroup of patients at extremely high risk. These patients need a more effective prophylactic regimen.