The geko device for reducing the risk of venous thromboembolism

No existing studies were identified on the cost impact of the geko device.

The sponsor submitted a de novo cost analysis using a decision tree model that estimated the cost associated with the geko device compared with no mechanical prophylaxis. The model population was patients for whom current mechanical methods of prophylaxis are impractical or contraindicated.

The decision tree structure was an amended version of the model from the NICE guideline on venous thromboembolism. The model assumed that patients treated with the geko device experienced a reduction in their baseline risk of deep vein thrombosis. Of the patients who went on to experience deep vein thrombosis, most would have either symptomatic or asymptomatic deep vein thrombosis but some would progress to pulmonary embolism. A proportion of patients with deep vein thrombosis also experienced post-thrombotic syndrome, a permanent comorbidity that could generate costs over the patient's lifetime. Further, it was assumed that the patients who had a pulmonary embolism also had a risk of death. The time horizon for the decision tree was 1 year but the model also included the lifetime (15 years) cost of post-thrombotic syndrome. The External Assessment Centre stated that it believed the model structure captured the clinical pathway of care, assumptions and health states in an appropriate manner for the evaluation.

Most of the clinical parameters were based on the NICE guideline on venous thromboembolism. The key assumptions for clinical parameters used in the model were:

• The underlying risk of deep vein thrombosis was 29.1% with no prophylaxis (this was based on the average risk of deep vein thrombosis for all surgical-related patients according to the NICE guideline on venous thromboembolism).

• The proportion of deep vein thrombosis progressing to a pulmonary embolism was 10.5%.

• There was a 6% chance of pulmonary embolism causing death. No other mortality cause was considered.

• The relative risk of a deep vein thrombosis after treatment with the geko device was 0.39.

• Post-thrombotic syndrome occurred in 25% of patients with symptomatic deep vein thrombosis or a pulmonary embolism and 15% of patients with asymptomatic deep vein thrombosis.

No evidence was available for the reduction in relative risk of deep vein thrombosis associated with the use of the geko device. The sponsor's assumption of a relative risk of 0.39 was based on the incidence of subclinical deep vein thrombosis after the use of neuromuscular electrostimulation as reported in Browse & Negus (1970). The sponsor stated that this was a conservative assumption and further justified this because the value fell within the range (0.31 to 0.58) identified for intermittent pneumatic compression in the NICE guideline on venous thromboembolism. The External Assessment Centre disagreed with this assumption.

The cost of the geko device was £22 per pair exclusive of VAT. The cost of purchasing the device per course of 6 days, to treat both legs, was therefore £132.

In the sponsor's model, the cost per patient estimated for the geko device was £359 and for the comparator (no prophylaxis) it was £565, resulting in a cost saving for the geko device of £206 per patient. After correcting for an error in the hourly nursing cost, the External Assessment Centre calculated the cost saving per patient to be £197.

The sponsor conducted univariate, 2-way and probabilistic sensitivity analyses. The 3 factors that affected the cost analysis the most were the cost associated with post-thrombotic syndrome, the relative risk of deep vein thrombosis associated with the geko device as a form of prophylaxis, and the proportion of deep vein thromboses that are symptomatic. The probabilistic sensitivity analysis showed that the geko device remained cost saving in 99% of simulations performed, with a mean cost saving of about £200 per patient. The sponsor concluded that the geko device was cost saving compared with no prophylaxis. The External Assessment Centre, stated that, although it believed the underlying assumption on risk reduction to be flawed, the sensitivity analysis covered all the uncertain variables, was well performed and that the results supported the conclusions about cost savings from the submitted model.

The sponsor performed subgroup analysis in people for whom pharmacological prophylaxis is indicated and prescribed. An economic model was developed using values for the relative risk of deep vein thrombosis with pharmacological prophylaxis alone and with pharmacological prophylaxis plus the geko device of 0.14 and 0.02, respectively. Compared with pharmacological prophylaxis alone, the geko device in combination with pharmacological prophylaxis was cost saving for the first 2 days and cost neutral if used for 3 days. It was not estimated to be cost saving after more than 3 days of treatment, with an incremental cost of £69 after 6 days of treatment.