Accuratezza diagnostica di stenosi dei test di sorveglianza utilizzabili al letto del malato nelle fistole arterovenose

Vascular access guidelines recommend regular monitoring/surveillance for early detection of stenosis in arteriovenous fistulae (AVFs) and suggest that each unit establish its own program comprising one or more procedures, but no studies have been conducted to compare comprehensively the diagnostic performance of the different procedures adopted. Angiography and monitoring/surveillance tests were performed in 76 randomly-selected hemodialysis patients (pts) with native AVF (53 males, 23 females, aged 62 + 16 years) to compare diagnostic accuracy of clinical examination (monitoring), dynamic venous pressure at blood pump flow rate (Qb) of 200 ml/min (VP200), derived static venous pressure (VAPR), Qb/negative arterial pre-pump pressure at Qb of 400 ml/min (Qb/NAP400), ultrasound dilution (UD) access recirculation (R) and UD access blood flow rate (Qa) in detecting angiographically-proven, significant (>50 %) stenosis. AVF was located in the lower third of the forearm (dAVF) in 31 pts and in the upper forearm/elbow region in 45 (pAVF). Angiography identified a significant stenosis in 36 AVFs (27 dAVF, 11 pAVF). The diagnostic accuracy of these procedures was evaluated by Receiver Operating Characteristics (ROC) curve analysis and expressed as area under the curve (AUC). The only tests revealing discriminatory power for STin were Qa (AUC 0.82 + 0.979, p <0.001) and clinical examination (AUC 0.0.540 + 0.08, p 0.018). VAPR (AUC 0.93 + 0.05, p <0.001), VP200 (AUC 0.80 + 0.09, p 0.015) and clinical examination (AUC 0.79 + 0.12, p 0.028) were the only significant predictors of STout. An optimal combination of sensitivity (SE) and specificity (SP) for STin was observed for Qa <900 ml/min, followed by clinical examination, while the best diagnostic accuracy for STout was observed for VAPR >0.50 followed by clinical examination and VP200 >80 mmHg. Our study suggests that diagnostic accuracy of the various AVF surveillance techniques depends on the location of the stenosis, Qa being the best test for STin and VAPR for STout . Clinical examination is the only tool with good discriminatory power for stenosis regardless of its location, but it carries the drawback of overlooking a considerable number of stenotic AVFs.