Accuracy of the Ottawa score in risk stratification of recurrent venous thromboembolism in patients with cancer-associated venous thromboembolism. A systematic review and meta-analysis.

In patients with cancer-associated venous thromboembolism, knowledge on the estimated rate of recurrent events is important for clinical decision regarding anticoagulant therapy. The Ottawa score is a clinical prediction rule designed for this purpose, stratifying patients according to their risk of recurrent venous thromboembolism during the first 6 months of anticoagulation. We conducted a systematic review and meta-analysis of studies validating either the Ottawa score in its original or modified version. Two investigators independently reviewed the relevant articles published from 06/01/2012 to 12/15/2018 and indexed in MEDLINE and EMBASE. Nine eligible studies were identified including 14,963 patients. The original score classified 49.3% of the patients as high-risk, with a sensitivity of 0.7 (95% confidence interval 0.6-0.8), a 6-month pooled rate of recurrent venous thromboembolism of 18.6% (95% confidence interval 13.9-23.9). In the low-risk group, recurrence rate was 7.3% (95% confidence interval 3.4-12.5). The modified score classified 19.8% of the patients at low-risk, with a sensitivity of 0.9 (95% confidence interval 0.4-1.0) and a 6-month pooled rate of recurrent venous thromboembolism of 2.2% (95% confidence interval 1.6-2.9). In the high-risk group, recurrence rate was 10.1% (95% confidence interval 6.4-14.6). Limitations of our analysis included type and dosing of anticoagulant therapy. We conclude that new therapeutic strategies are needed in patients at high-risk for recurrent cancer-associated venous thromboembolism. Low-risk patients, as per the modified score, could be good candidates to oral anticoagulation (PROSPERO CRD42018099506).