Testing strategies for DVT identified

It suggests that there are two approaches, both involving a combination of clinical assessment, blood testing and ultrasound, that give the most clinically and cost-effective options for diagnosis of DVT in hospital. A survey of over 200 emergency departments carried out as part of the research found that while most hospitals had a testing protocol in place, there was great variation in practice. The strategies, published as part of the completed report, could provide a useful practical guide for medical staff to follow during DVT investigation. The study was published in the Health Technology Assessment journal and in the June issue of the Quarterly Journal of Medicine.

Led by Dr Steve Goodacre of the Medical Care Research Unit, University of Sheffield, the research team carried out a systematic review of existing research evidence to assess the performance of different non-invasive diagnostic tests for DVT. The team examined accuracy, and clinical and cost effectiveness of the different tests. They included clinical assessment (using a Wells scoring system), a blood test for D-dimer, plethysmography and rheography techniques, ultrasound, CT and MRI scanning, and venography, which is traditionally regarded as the reference standard. The researchers also sent surveys to 255 UK hospitals, asking them to describe current practice and availability of tests, and to identify any testing strategies already in place.

The researchers found that two particular strategies (referred to in the report as algorithms nine and 16), both using a combination of Wells score, D-dimer and above-knee ultrasound, were the most cost-effective, and would be feasible in UKhospitals without substantial reorganisation of services. One strategy (algorithm 16) involved discharging patients with a low or intermediate Wells score and negative D-dimer; ultrasound for those with a high score or positive D-dimer; and repeat scanning for those with positive D-dimer and a high Wells score but negative initial scan. Amore expensive but similar strategy (algorithm nine) would involve repeat ultrasound for all those with a negative initial scan.

Survey responses established that most hospitals were using some sort of testing strategy, and of the 61 hospitals that provided details of their strategy, three-quarters were using a combination of the above tests. However, there were differences in the protocols they followed. Some advised no further testing for patients with a low Wells score, whereas others advised Ddimer or ultrasound.

“The algorithms identified in the study provide a clear guide that could be followed by NHS service providers to ensure a consistent approach,” comments Dr Goodacre. “More research could be carried out to investigate the practicalities of implementing them throughout the NHS, such as how the algorithms perform in different groups of patients and when they are implemented by different providers.”