Background / History
Henry Ford Health Systems in Detroit is responsible for the Greenfield Health Systems, comprising 17 dialysis centers. While the staff recognized the importance of maintaining a patent AV vascular access, they could not afford to devote several staff members to testing each access every month. Furthermore, testing once a month was not frequent enough to provide adequate warning for patients whose stenosis was growing rapidly.
To address this issue, the HFHS staff looked for ways to use the pressure data that was already recorded during each treatment as an indicator for stenosis. While these pressure readings are by themselves not an effective indicator, by correcting them for the blood flow, hematocrit, and even gravity, they were able to derive the pressure at the tip of the needle. These factors were formalized as an algorithm. Application of the algorithm to treatment data resulted in clear trends in access pressure.
Since the results from a single treatment can be affected by extraneous factors such as bad needle placement, a positive result would be defined as three consecutive values above threshold. To determine the ideal threshold, test results based on a variety of thresholds were compared to historical intervention data for the same test population. The value chosen as the threshold optimized true positives and minimized the incidence of both false positives, where the patient would be referred with insignificant stenosis, and false negatives, when it was too late to take preventive action.
Following the trend of these alerts each week provides an indication of access dysfunction that can allow clinical staff the early warning necessary to make a timely referral.
A large study was conducted and published in 2001. The conclusion:
“After 3 months, sensitivity and specificity for detection of a graft event were 70% ± 8% and 88% ± 2% and increased to 74% ± 5% and 92% ± 3% at 6 months, respectively. ”
Additional studies were conducted showing equal efficacy for patients with fistulas. The FDA approved the device for general use in 2003, and the product was then commercialized by Vasc-Alert, LLC. A patent was issued in 2009. Vasc-Alert is currently producing reports for over 20,000 patients on a weekly basis.
The ability to prevent serious thrombosis complications using existing data helps organizations and their patients in numerous ways – clinically, administratively, and financially. To learn more about the many benefits of Vasc-Alert, click here.