All Surveillance Methods Are Not Comparable
A serious error in the 2019 proposed National Kidney Foundation’s (NKF) Kidney Disease Outcomes Quality Initiative (KDOQI) is their grouping of all methods of vascular access surveillance as comparable. They are not! For instance, venous pressure measurements (Vasc Alert), can identify an outflow vascular access stenosis but cannot detect an inflow stenosis. In contrast, Transonic’s indicator dilution measurements can identify inflow and outflow stenoses as well as stenoses between the needles. This is significant because Asif et al, reported in his 2005 study “Inflow stenosis in arteriovenous fistulas and grafts: a multicenter, prospective study,” that 35% of vascular accesses sent for intervention do have inflow stenosis.1
It was not long after its introduction in 1995, that Transonic’s ultrasound dilution technology was recognized as the gold standard measurement of access flow. In her 2002 publication in Renal Replacement Therapy, Are Hemodialysis Access Flow Measurements by Ultrasound Dilution the Standard of Care for Access Surveillance2, JS Garland concluded:
“Ultrasound indicator dilution is the current Gold Standard for measurement of vascular access recirculation and access flow”;2
- Ultrasound indicator dilution is the method of choice for monthly surveillance of vascular access grafts in adherence to NKF-K/DOQI guidelines
- Available evidence suggests that access flow measurements are the best tests currently available to screen for access dysfunction.
- Monthly surveillance is a cost-effective strategy.
Her conclusions were echoed by a Lopot in his study entitled, Comparison of Different Techniques of Hemodialysis Vascular Access Flow Evaluation3 the following year.
“Very high reproducibility and negligible impact of flow (Qb) on vascular access flow (QVA) determination justifies the current ultrasound dilution status as a reference method in QVA evaluation.” Lopot et al1
In the Lopot study, Transonic’s ultrasound dilution technology was used as the reference gold standard method against which other methods were compared. Methods compared included Duplex Doppler (DD), thermodilution (BTM Fresenius, Europe) and three Critline Hemametrics optodilutional measurements. The study concluded that all methods ,other than Transonic’s ultrasound dilution, with the exception of BTM thermodilution, fall short of being recommended as viable methods to measure vascular access blood flow. The authors acknowledged that BTM’s thermodilution correlated well with ultrasound dilution and could be used as a viable alternative method.
In another study4, “Comparison of Different Methods to Assess Fistula Flow,” by Eloot three access flow (AF) monitoring techniques: ultrasound dilution, blood temperature monitoring (BTM), and online clearance monitoring (OCM) were evaluated. The impact of the time of a dialyzer blood flow (QB) measurement and the patient’s position was also investigated. The study concluded that access flows measured ultrasound dilution and BTM correlated well and may be measured at flows 200-300 mL/min in all measured positions. Online clearance monitoring (OCM) was unreliable for measuring AF and was therefore further omitted.
These two studies underscore the fact that all surveillance methods are not equal or comparable. For the proposed KDOQI Guidelines to treat all surveillance technologies as the same ignores 20+ years of science and is a serious mistake.