Utility of a recurrence prediction tool (DASH score) at a single centre after unprovoked venous thromboembolism: patient uptake of the tool and short term risks of stopping anticoagulation

Excerpt

The optimal duration of anticoagulation after unprovoked venous thromboembolism (VTE) following the initial 3–6 months of anticoagulation is still unknown and often debated [1, 2]. At our centre we have previously used the DASH score (D-dimer 1 month after stopping anticoagulation (2 points if positive), age (1 point if ≤ 50 years), sex (1 point if male) and use of oestrogen hormonal therapy (− 2 points)) for patients with unprovoked VTE to help guide discussions about the balance of risks of long-term anticoagulation, and we have previously published the clinical outcomes (in terms of VTE recurrence) from our clinic [3‐5]. The DASH score was used at our thrombophilia clinic from 2013 to 2017. Here we present data about the uptake of the tool amongst patients/clinicians, reasons why it may not have been utilised and also the short term thrombotic risks of stopping anticoagulation in order to have a D-dimer performed for the DASH score. This was a retrospective chart review of patients managed in the thrombophilia clinic at Cambridge University Hospitals NHS Foundation Trust between 2013 and 2017. Locally all patients with unprovoked VTE are referred to the clinic and seen 3–6 months after the VTE to make an individualised treatment decision on the benefits and risks of either stopping or continuing long-term anticoagulation. Only patients with proximal lower limb deep vein thrombosis or pulmonary embolism have been included. The methods have previously been described in detail elsewhere [4, 5]. 452 patients were identified and 5 were excluded, as there was no information available for any further analysis, therefore 447 were included for final analysis. 145 (32.4%) patients continued anticoagulation long-term without a DASH score being calculated. 31 (6.9%) patients did not have a DASH score calculated and stopped anticoagulation. 271 (60.6%) patients had a DASH score calculated and of these 145 had a score of ≤ 1 and stopped anticoagulation (32.4%), 32 (7.2%) had a score of 2 or 3 and stopped anticoagulation and 94 patients (21.0%) continued anti-coagulation long-term (Fig. 1). Of the 239 patients that continued long-term, reasons for this included the DASH score being raised (≥ 2) in 94 patients (39.3% of the 239) whilst there were a variety of recorded reasons in other patients (Table 1). Of the 271 patients that stopped anticoagulation to have a DASH score calculated, 4 had a venous thromboembolism whilst they awaited the D-dimer blood test and follow-up clinic review; a recurrence rate of 1.5% in this window of a few weeks. This report has 2 main findings of note. Firstly, approximately one-third of patients (1/3) continue anticoagulation for unprovoked VTE rather than have a DASH score calculated; the utility of the score is therefore limited to a more defined sub-group where it is felt there is clinical equipoise about long-term decision making with regards to long-term anticoagulant management. The reasons for continuing anticoagulation, due to patient preference and other defined VTE risk factors, are diverse (Table 1) and these factors are not counted in the DASH score and therefore limit its applicability to patients deciding on long-term anticoagulation. Secondly, patients should be warned about a small thrombotic risk in the time period after they have stopped anticoagulation should they decide to do so in order to have an off treatment D-dimer performed. In the prospective study examining the use of the HERDOO2 score for VTE risk recurrence prediction, 2785 patients were enrolled, 2779 (99.7%) were classified with the HERDOO2 score and 1833 (65.8%) continued anticoagulation, although using this tool men cannot stop anticoagulation due to a high recurrence risk irrespective of the HERDOO2 score, based on gender alone [6]. It is difficult to make a direct comparison to our data because patients that wished to continue anticoagulation may not have entered the study at all (6325 were assessed for eligibility in the prospective HERDOO2 study) and also our data is a single centre retrospective study reflecting local practices. Notably from our data, of patients that had a DASH score, 54% could discontinue anticoagulation and this included men and women, however our previous work showed that these patients did have a VTE recurrence risk > 5% per annum [4, 5]. In summary our data shows that a significant proportion of patients will continue anticoagulation due to preference or clinical risks, without the use of a risk prediction score. When patients do stop anticoagulation for 1 month to have a D-dimer performed, to help guide VTE recurrence risk, they should be counselled about the small risk of a VTE in that time. Further research is needed to determine patients with unprovoked VTE that would most benefit from long-term anticoagulation.

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