[Surveillance of arteriovenous fistula: new answers to an old problem]

Arteriovenous fistula (AVF) surveillance is pivotal to early detection of stenosis, in order to avoid subsequent thrombosis. Access flow measurement is the method recommended by the available guidelines. With respect to grafts, in native AVF the best thresholds of access flow intervention, optimal timing of monitoring and cost-effectiveness are still debated. In fact, monthly measurement of access flow is difficult to obtain in most modern hemodialysis units. Moreover, in native AVF it is not always possible to perform the gold-standard surveillance methods. Finally, clinical evaluation is not enough to identify the small number of patients at risk of stenosis. The QB stress test (QBST) is a new and simple screening test that was created to identify inflow stenosis and thereby malfunctioning AVF. QBST shows a good correlation with access flow measurements obtained by the ultrasound dilution technique. Moreover, the test can be performed in every type of native AVF. Patients with a positive QBST result had a lower access flow than patients with a negative QBST result (433+-203 vs 1168+-681 mL/min, p<0.0001). The positive predictive value for inflow stenosis was 76.3%. During a 22-month followup, we were able to achieve a low thrombosis rate (1.5 instances of thrombosis per 100 patient-years). In conclusion, adding QBST to the clinical evaluation could offer a new solution for the long-standing AVF surveillance problem.