Validation of the clinical prediction rule for recurrent venous thromboembolism in cancer patients: the Ottawa score.

PURPOSE: Recently, a clinical prediction rule for recurrent venous thromboembolism (VTE) in cancer patients, named Ottawa score, was derived to individualize treatments with different intensities. It is composed of four variables including sex, primary tumor site, tumor stage, and prior history of VTE. The objective of this study was to validate the Ottawa score in an independent patient population in a tertiary hospital in Korea.
METHODS: Medical records of consecutive adult patients (>18 years) with active malignancy and newly diagnosed VTE from January 1, 2006 to December 31, 2010 were analyzed. Using the same definition of predictor variables in the original derivation study, patients were divided into low (score ≤ 0) and high (score ≥ 1) risk groups for recurrent VTE, and their actual recurrence rate were analyzed.
RESULTS: Of the 546 patients with newly diagnosed VTE, 99 (18.1 %) had recurrent VTE during the follow-up period. In the low-risk group, 34 (13.2 %) had recurrence, compared to 65 (22.4 %) in the high-risk group. Ottawa score's performance showed 66 % sensitivity, 50 % specificity, 22 % positive predictive value, and 87 % negative predictive value in our validation cohort.
CONCLUSION: We were not able to accurately ascertain the relevance of the Ottawa score in our validation cohort. Future validation studies, including a more diverse patient population with different cancer predominance, are warranted.