The Rise and Fall of Access Blood Flow Surveillance in Arteriovenous Fistulas

Vascular access blood flow (Qa) surveillance has been described as a typical false paradigm, an example of how new tests are sometimes adopted even without good-quality evidence of their benefits. This may be true for grafts, but not necessarily for arteriovenous fistulas. We reviewed the literature on Qa surveillance in fistulas to see whether it complies with the World Health Organization’s criteria for screening tests. Measuring Qa has a fairly good reproduc-ibility. Qa shows an excellent-to-good accuracy for stenosis being the only bedside screening test that achieves a very high sensitivity while retaining a fair-to-good positive pre-dictive value for Qa thresholds of 600 ml/minute or higher associated with a > 25% drop in Qa, or findings suggestingstenosis on physical examination. The accuracy of Qa in predicting thrombosis is hard to establish because of the heterogeneity of published studies, though a Qa of 300 ml/minute seems the most reliable cutoff. Qa surveillanceaffords a significant 2- to 3-fold reduction in the risk of thrombosis by comparison with clinical monitoring alone when Qa criteria highly sensitive to stenosis are considered, regardless of the study design (randomized controlled trials, cohort studies with concurrent or historic controls). Usinghighly sensitive Qa screening criteria also halves the risk of access loss, although this effect is not statistically signifi-cant. Our analysis strongly suggests that Qa surveillance is an effective method for screening mature fistulas, thoughfurther, appropriately designed studies are needed to fully elucidate its benefits and cost effectiveness.