The changing face of venous thromboembolism management in England

Oral Anticoagulation Therapy for Venous Thromboembolism in Norway: Time Trends and Treatment Patterns

PURPOSE

Data describing treatment patterns of patients with venous thromboembolism (VTE) patients in Scandinavia are scarce. This study sought to address this scarcity by describing demographic and clinical characteristics, trends in the use of oral anticoagulants (OACs), and treatment patterns in patients treated for VTE in Norway between 2013 and 2017.

METHODS

Using data from Norway's nationwide registries, a cohort study included patients newly (after 2008) treated OACs who were diagnosed with VTE between January 2013 and December 2017 and were dispensed an OAC (warfarin, apixaban, rivaroxaban, dabigatran, or edoxaban) within 30 days. Patient characteristics and the percentage of patients with VTE who initiated treatment with each OAC for each calendar year were reported. Initial therapy persistence was assessed using Kaplan-Meier curves and compared between the OAC groups using the log-rank test.

FINDINGS

The comorbidity burden was similar between patients taking warfarin and those taking apixaban but lower among patients taking rivaroxaban. Direct oral anticoagulant (DOAC) use increased from 33.2% to 93.6% during the study period, whereas warfarin use decreased. Persistence was higher in the apixaban cohort compared with the warfarin cohort, with the difference mostly apparent after 6 months, whereas persistence was similar between the patients taking rivaroxaban and those taking warfarin.

IMPLICATIONS

Between 2013 and 2017, DOAC use among patients with VTEs increased markedly in Norway, whereas the use of warfarin decreased. Patients taking apixaban had higher persistence compared with those taking warfarin, whereas patients taking warfarin and those taking rivaroxaban had similar persistence. Further studies with longer follow-up are required to examine the use of extended OAC treatment for VTE.

Validation of venous thromboembolism diagnoses in patients receiving rivaroxaban or warfarin in The Health Improvement Network

Purpose

To describe the effect that validation of venous thromboembolism (VTE) coded entries in the health improvement network (THIN) has on incidence rates of VTE among a cohort of rivaroxaban/warfarin users.

Methods

Among 36 701 individuals with a first prescription for rivaroxaban/warfarin between 2012 and 2015, we performed a two‐step VTE case identification process followed by a two‐step case validation process involving manual review of patient records. A valid case required a coded entry for VTE at some point after their first rivaroxaban/warfarin prescription with evidence of referral/hospitalization either as a coded entry or entered as free text. Positive predictive values (PPVs) with 95% confidence intervals (CIs) were calculated using validated cases as the gold standard. Incidence rates were calculated per 1000 person‐years with 95% CIs.

Results

We identified 2166 patients with a coded entry of VTE after their initial rivaroxaban/warfarin prescription; incidence rate of 45.31 per 1000 person‐years (95% CI: 43.49‐47.22). After manual review of patient records including the free text, there were 712 incident VTE cases; incidence rate of 14.90 per 1000 person‐years (95% CI: 13.85‐16.02). The PPV for coded entries of VTE alone was 32.9%, and the PPV for coded entries of VTE with a coded entry of referral/hospitalization was 39.8%; this increased to 69.6% after manual review of coded clinical entries in patient records.

Conclusions

Among rivaroxaban/warfarin users in THIN, valid VTE case identification requires manual review of patient records including the free text to prevent outcome misclassification and substantial overestimation of VTE incidence rates.