External validation of a prognostic score to identify low-risk outpatients with acute deep venous thrombosis in the lower limbs.

Background: Current clinical guidelines suggest home treatment for patients diagnosed with acute deep venous thrombosis (DVT). A prognostic score has been proposed to identify low-risk patients; however, its validation remains limited.

Method: This prospective observational study aimed to externally validate the prognostic score in selecting low-risk outpatients with acute DVT in the lower limbs. Consecutive outpatients diagnosed with acute DVT in a tertiary hospital were included. The score included 6 variables: heart failure, kidney failure, recent major bleeding, altered platelet count, immobilization, and cancer. The primary outcome was the incidence of a composite outcome, including confirmed diagnosis of PE, major bleeding, or all-cause death at 7 days. Patients meeting zero criteria were considered low risk.

Results: Among the 1035 patients included, 485 (46.9 %) met zero criteria. Of these, 0.2 % (95 % CI 0.0-1.1 %) and 0.4 % (95 % CI, 0.0-1.5 %) patients experienced the composite outcome at 7 and 30 days, respectively. Among patients who met 1 or more criteria for admission, 344 patients (62.5 %) were discharged. Among these, the composite outcome at 7 and 30 days occurred in 2 (0.6 %) and 5 (1.4 %) patients, respectively. The C-statistics of the score were 0.68 (95 % CI, 0.57-0.79) and 0.69 (95 % CI, 0.64-0.76) at 7 and 30 days, respectively.

Conclusion: This study demonstrates the efficacy of the prognostic score in identifying low-risk outpatients with acute DVT. It also suggests that a considerable proportion of patients with acute DVT may benefit from outpatient treatment despite having some risk criteria, highlighting the potential for optimizing ambulatory care pathways.