AVIDIN AND (111) IN-LABELED BIOTIN SCAN - A NEW RADIOISOTOPIC METHOD FOR LOCALIZING VASCULAR GRAFT INFECTION

Objectives: To evaluate a new imaging technique, for diagnosis of pros thetic vascular graft infection. Avidin is a protein which accumulates nonspecifically at sites of inflammation or infection. Due to its ext remely low dissociation constant with biotin sites of infection can be imaged, using avidin as a pre-target, followed by injection of In-111 -labelled biotin. This technique is much simpler than the common scint igraphic methods which employ labelling of blood components and its ta rget-to-background ratio is greater than the methods employing radiola belled proteins. Design: Prospective clinical study. Setting: A single department of vascular surgery and one of nuclear medicine of a North ern Italian hospital. Materials: Between May 1993 and May 1994, 31 gra fts in 26 patients were studied; the series included 23 men and three women with a mean age of 65.5 years (range 54-76 years). The prostheti c graft (Dacron -16, ePTFE-15) were: aortoaortic 5, aortobifemoral 15, aortoiliac 1, and femoropopliteal 10. Sixteen patients were suspected of having a vascular graft infection (Group A), the other 10 patients served as controls (Group B). 20 mg of Avidin were injected iv, follo wed 24 h later by i.v. injection of 500 mu g of Biotin labelled with 7 4 MBq of In-111. Chief outcome measures: Whole-body imaging teas perfo rmed at 10 min and 2 h post-injection, along with SPECT imaging when i ndicated. Scan results were correlated with the traditional imaging mo dalities and the clinical outcome of the patients. Main results: In Gr oup A: two patients (three grafts) were excluded from the study, there were six true-positives, one false-positive and 11 true-negatives. Re sults in Group B: 10 true-negatives. The overall sensitivity was 100%, the specificity 95%, the accuracy 96%, the positive predictive value 86% nl?and the negative predictive value 100%. Conclusions: These data suggest that Avidin/In-111-lnbelled Biotin scintigraphy is a useful n on invasive diagnostic method for early diagnosis of suspected prosthe tic vascular graft infection.