Department of Medicine, Renal Unit, Azienda Ospedaliera Universitaria Integrata di Verona, Verona, Italy.
Department of Public Health and Community Medicine, University of Verona, Verona, Italy.
Nephrol Dial Transplant. 2019 Jul 1;34(7):1102-1106. doi: 10.1093/ndt/gfz003.
Guidelines recommend regular screening of mature arteriovenous fistulas (AVFs) for preemptive repair of significant stenosis (≥50% lumen reduction) at high risk of thrombosis, identifiable from clinical signs of access dysfunction (monitoring) or by measuring access blood flow (Qa surveillance), which also enables stenosis detection in functional accesses. To compare the value of Qa surveillance versus monitoring, a meta-analysis was performed on the randomized controlled trials (RCTs) comparing the two screening strategies. It emerged that correcting stenosis identified by Qa surveillance significantly halved the risk of thrombosis [relative risk (RR) = 0.51, 95% confidence interval (CI) 0.35-0.73] and access loss (RR = 0.47, 95% CI 0.28-0.80) in comparison with intervention prompted by clinical signs of access dysfunction. One small RCT aiming to identify an optimal Qa threshold showed that stenosis repair at Qa >500 mL/min produced a significant 3-fold reduction in the risk of thrombosis (RR = 0.37, 95% CI 0.12-0.97) and access loss (RR = 0.36, 95% CI 0.09-0.99) in comparison with intervening when Qa dropped to <400 mL/min as per guidelines. To test the real-world benefits of Qa surveillance, the expected RCT-based thrombosis and access loss rates with Qa surveillance were compared with the rates with monitoring reported in observational studies: the expected thrombosis and access loss rates with surveillance were only lower than with monitoring when a Qa >500 mL/min was considered (2.4, 95% CI 1.0-4.6 and 2.2, 95% CI 0.7-5.0 versus 9.4, 95% CI 7.4-11.3 and 10.3, 95% CI 7.7-13.4 events per 100 AVFs-year, P ≤ 0.024), suggesting that in clinical practice adopting Qa surveillance may only be worthwhile at centres with high thrombosis and access loss rates associated with monitoring, and adopting Qa thresholds >500 mL/min for elective stenosis repair.
指南建议对成熟的动静脉瘘（AVF）进行定期筛查，以便对高血栓风险（可通过临床评估发现）的显著狭窄（≥50%管腔减少）进行预防性修复，或通过测量血流量（Qa 监测）发现狭窄，这也可在功能正常的瘘管中发现狭窄。为了比较 Qa 监测和临床评估的价值，我们对比较两种筛查策略的随机对照试验（RCT）进行了荟萃分析。结果表明，与根据临床评估发现狭窄并进行干预相比，通过 Qa 监测发现并纠正狭窄可使血栓形成的风险降低一半[相对风险（RR）=0.51，95%置信区间（CI）0.35-0.73]，并降低通路丧失的风险（RR=0.47，95%CI 0.28-0.80）。一项旨在确定最佳 Qa 阈值的小型 RCT 表明，当 Qa 值>500ml/min 时进行狭窄修复，可使血栓形成风险（RR=0.37，95%CI 0.12-0.97）和通路丧失风险（RR=0.36，95%CI 0.09-0.99）降低 3 倍，与根据指南在 Qa 下降到<400ml/min 时进行干预相比。为了检验 Qa 监测的实际效果，我们比较了 Qa 监测的 RCT 预计血栓形成和通路丧失率与观察性研究中监测报告的实际发生率：仅当 Qa 值>500ml/min 时，监测的预计血栓形成和通路丧失率才低于临床评估[9.4，95%CI 7.4-11.3 和 10.3，95%CI 7.7-13.4 事件/100AVF 年]，而当 Qa 值<500ml/min 时，监测的预计血栓形成和通路丧失率更高（2.4，95%CI 1.0-4.6 和 2.2，95%CI 0.7-5.0），这表明在临床实践中，只有在与监测相关的血栓形成和通路丧失率较高的中心，采用 Qa 监测才可能有价值，并且对于择期狭窄修复，应采用>500ml/min 的 Qa 阈值。
