The City Health Care Partnership based in Hull have been using Roche Cobas quantitative point-of-care (POC) D-dimer tests to aid diagnosis of DVTs since 2013.
Recently published NG158 venous thromboembolic diseases: diagnosis, management and thrombophilia testing recommends considering the use of POC D-dimer tests as an alternative to laboratory D-dimer tests.
Since implementing the tests, the main advantage is the reduction in time from the person presenting, to diagnosis and receiving treatment. Other advantages include a reduction in unnecessary interim anticoagulant treatment (reducing risk of potential adverse effects), avoiding unnecessary investigations such as ultrasound scans and consequently saving money.
Example
Aims and objectives
NICE guidance states that if a D-dimer test cannot be obtained within 4 hours, interim anticoagulation should be given. If a person has a low likelihood of having a DVT, indicated by a Wells score of 1 or lower, then a negative D-dimer means there is no need for an ultrasound scan.
Therefore, the aims of implementing POC D-dimer tests were to a) reduce time from presenting to diagnosis and treatment, b) reduce the amount of interim anticoagulation, c) reduce the amount of ultrasound scans and d) save money.
Reasons for implementing your project
This nurse-led community DVT service based in a health centre covers a population of 0.5 million across Hull and East Riding. It is commissioned by Hull CCG.
People who present with suspected deep vein thrombosis should have all diagnostic investigations completed as soon as possible. A D-dimer test is an important part of the diagnostic pathway and typically, this would be obtained via laboratory testing. However, as a community-based DVT service without a dedicated laboratory service, we have to utilise laboratory facilities in secondary care, resulting in delays in obtaining the result.
Including the time taken to deliver the samples to the hospital, the average time to receive the result was between 4 to 6 hours, which meant the patient would need to be given interim therapeutic anticoagulation. As ultrasound scanning is available onsite, it also meant there was a tendency to scan patients whilst waiting for the D-dimer result. As NICE recommends that people with a low likelihood of DVT and a negative D-dimer test do not need scanning, this meant some patients were receiving unnecessary scans.
How did you implement the project
A cost analysis of implementing POC D-dimer tests was initially undertaken. The initial outlay included the cost of the machines (approx. £1000 each at the time of purchasing). In our service, there are up to 2 nurses at any one time seeing patients, therefore 2 machines were purchased. As the machines are portable, this also allows for one machine to be taken off-site and used at home visits, although currently, this isn’t a service which is required in our area.
Ongoing costs include consumables such as the cassette used in the machine, pipettes and quality control items. When all these costs were taken into account and compared to the costs associated with obtaining laboratory tests, the cost difference was found to be insignificant.
A venous blood sample is required for the test and all nurses in the service are trained to do this. Using the machine is very straight forward and it takes 8 minutes to get a test result. Staff in our service were initially provided training by Roche, but this training has since been transferred into a SOP which all new staff follow.
Key findings
We see approximately 1500-2000 people a year with suspected DVT. With POC D-dimer tests in place, the average time from a person presenting, to diagnosis and treatment is approximately 1 hour, compared to the 4-6 hours it previously took to receive the D-dimer result, plus the additional time then required to undertake further investigations if needed. This reduction in time to diagnosis means the patient’s journey through the service is more efficient and time to treatment, when required, is reduced.
Those with a low likelihood of DVT and a negative D-dimer test no longer undergo unnecessary scans, resulting in a cost saving. More importantly for the patient, very few people receive interim therapeutic anticoagulation, as this is only required if the test result is going to take longer than 4 hours. Only those who attend late may require this if investigations cannot be completed and they have to return the following day. As well as the cost savings, this reduces the risks involved with exposing people to anticoagulation potentially unnecessarily.
Key learning points
Implementation of POC D-dimer tests within our dedicated community DVT service was easy – once the cost difference between the POC tests and laboratory tests were shown to be insignificant, all stakeholders immediately saw the benefit to patients and were supportive of using them. However, we can also see the benefit of other non-dedicated services using these tests, and we would suggest considering the following:
- Consider the number of machines required. As our service is a dedicated DVT service, it made sense to invest in more than one machine to accommodate each clinic room. However, as the tests are quick, many services would find one machine adequate.
- Consideration could be given to purchasing a machine and sharing the cost and it’s use between a group of GPs or as part of a primary care network.
- Time is of the essence when diagnosing DVT and interim anticoagulation therapy is necessary if diagnosis is delayed. If you are in a location where laboratory testing cannot be done within 4 hours, use of POC D-dimer tests may reduce your use of anticoagulation therapy. This avoids people being exposed unnecessarily to anticoagulation and the risks that are associated with this. This may also lead to cost savings.