Is there value in repeating lower limb doppler ultrasound for suspected deep venous thrombosis, without clinical reassessment?

ABSTRACT

Category Ultrasound Purpose: Lower limb deep vein thrombosis (DVT) causes significant morbidity, posing a diagnostic challenge. The National Institute for Health and Care Excellence (NICE) advises repeat ultrasound evaluation six to eight days after an initial negative scan, if the Well’s Score is ≥2 and D-dimer >230 ng/ml. Occasionally, in our trust, patients in whom symptoms improved have returned for repeat scans. We question the value in rescanning without clinical reassessment, aiming to investigate a) the frequency of positive repeat scans and b) factors increasing the likelihood of DVT on the second scan. Our aims evolved in the context of the coronavirus (COVID-19) pandemic. Methods and materials We evaluated 13 months of data (January 2018 to January 2019). Patients with two scans within six weeks (no DVT on initial scan and arranged as per NICE guidance) were selected. We retrospectively analysed data from the trust’s ultrasound database, the CDN radiology information system (CRIS) and electronic patient records system (PPM+). We analysed five months of data following the first UK COVID-19 lockdown (23 March 2020) to evaluate how the positive yield was impacted. Results: Pre-pandemic, of 1,006 patients (412 male, 594 female;age range 18–101), 19 had repeat ultrasound scans that were positive (1.9%). Following the UK national lockdown, of 170 patients, 11 were positive (6.5%). Conclusion: In the pre-lockdown setting, positive yield after a negative ultrasound is low (<2%). We support a clinical reassessment before rescan, combining persistent clinical suspicion with positive D-dimer. In a pandemic context, this has improved diagnostic yield (6.5%, p<0.01);however, long-term safety data is required.