Objective: The resistance index (RI) and the blood flow volume (Qa) are the most used Doppler ultrasound (DUS) parameters to identify the presence of stenosis in arteriovenous fistula (AVF). However, the reliability of these indexes is now matter of concern, particularly in predicting subsequent thrombosis. In this study, we aimed at testing the diagnostic capacity of the Qa/RI ratio (Q_x) for the early identification of AVF stenosis and for thrombosis risk stratification.

Methods: From a multicentre source population of 336 HD patients, we identified 119 patients presenting at least one "alarm sign" for clinical suspicious of stenosis. Patients were therefore categorized by DUS as stenotic (n = 60) or not-stenotic (n = 59) and prospectively followed. Q_a, RI, and Q_X, together with various clinical and laboratory parameters, were recorded.

Results: Qa and Qx were significantly higher while RI was significantly lower in non-stenotic vs. stenotic patients (p < 0.001 for each comparison). At ROC analyses, Qx had the best discriminatory power in identifying the presence of stenosis as compared to Qa and RI (AUCs 0.976 vs. 0.953 and 0.804; p = 0.037 and p < 0.0001, respectively). During follow-up, we registered 30 thrombotic events with an incidence rate of 12.65 (95% CI 8.54-18.06) per 100 patients/year. In Cox-regression proportional hazard models, Qx showed a better capacity to predict thrombosis occurrence as compared to Qa (difference between c-indexes: 0.012; 95% CI 0.004-0.01).

Conclusions: In chronic haemodialysis patients, Qx might represent a more reliable and valid indicator for the early identification of stenotic AVFs and for predicting the risk of following thrombosis.

Source: Colombo A, Provenzano M, Rivoli L, et al. Utility of Blood Flow/Resistance Index Ratio (Qx) as a Marker of Stenosis and Future Thrombotic Events in Native Arteriovenous Fistulas[J]. Front Surg, 2020, 7:604347. DOI: 10.3389/fsurg.2020.604347. 

目的：阻力指数（RI）和血流量（Qa）是最常用的多普勒超声（DUS）参数，用于识别动静脉内瘘（AVF）中是否存在狭窄。但是，这些指标的可靠性现在值得关注，尤其是在预测随后的血栓形成时。在这项研究中，我们旨在测试Qa / RI比（Qx）对AVF狭窄的早期识别和血栓形成风险分层的诊断能力。

方法：从336名HD患者的多中心来源人群中，我们鉴定出119名表现出至少一个“警报征兆”的临床可疑狭窄患者。因此，根据多普勒超声，将患者分为狭窄（n = 60）或非狭窄（n = 59）两组，并进行前瞻性随访。记录Qa，RI和QX，以及各种临床和实验室参数。

结果：与狭窄组患者相比，非狭窄组患者Qa和Qx显着较高，而RI则显着较低（每次比较p <0.001）。在ROC分析中，与Qa和RI相比，Qx在识别狭窄是否存在方面具有最佳区分能力（AUC分别为0.976、0.953和0.804； p = 0.037和p <0.0001）。在随访期间，我们登记了30例血栓事件，每100例患者/年的发生率为12.65（95％CI 8.54-18.06）。在Cox回归比例风险模型中，与Qa相比，Qx具有更好的预测血栓形成的能力（c指标之间的差异：0.012； 95％CI 0.004-0.01）。

结论：在慢性血液透析患者中​​，Qx可能是早期识别狭窄性AVF和预测血栓形成风险的更可靠和有效的指标。

启发：一项指标能力有限时，组合可能是一种新的思路。