Clinical utility of technetium-99m-labelled leukocyte scan in diagnosis of vascular infections

The diagnosis of vascular graft infections and infected aneurysms via conventional methods such as computed tomography (CT) and ultrasound (US) can often be challenging. Nuclear medicine imaging techniques can detect infection in these difficult cases. We aim to evaluate the diagnostic value of technetium-99m-labelled leukocyte scans in diagnosing vascular graft infections in our centre.

There were 164 patient-scans identified over a 16-year period. The electronic clinical records, laboratory findings and radiology of these patients were reviewed. An adapted case definition of infection was defined using the criteria proposed by the Management of Aortic Graft Infection Collaboration. There were 43 patients identified to have vascular indications and had sufficient information to be divided into infected and non-infected groups. Imaging and reports of the leucocyte scans in these patients were analysed to calculate specificity and sensitivity.

Overall sensitivity of leucocyte scans to detect vascular infection was 78.1% and specificity of 81.8% with a positive likelihood ratio of 4.30 and negative likelihood ratio of 0.27. Two false positives in patients with aortic grafts; one patient possibly had concurrent gastrointestinal infection and continued antibiotic treatment. The other patient had persistent uptake around an endoleak and was treated with lifelong antibiotics for aortic vascular graft infection on the basis of the leucocyte scan; no other clinical or laboratory evidence was found to fulfil the case definition of the vascular graft infection.

Technetium-99m-labelled leukocyte scan can be a useful adjuvant test in diagnosing suspected vascular infections in this uncommon presentation.