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American Society of Diagnostic and Interventional Nephrology Section Editor: Stephen Ash: Thresholds for Significant Decrease in Hemodialysis Access Blood Flow
Author(s) -
Ram Sunanda J.,
Nassar Raja,
Sharaf Rashid,
Magnasco Alberto,
Jones Steven A.,
Paulson William D.
Publication year - 2005
Publication title -
seminars in dialysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 78
eISSN - 1525-139X
pISSN - 0894-0959
DOI - 10.1111/j.1525-139x.2005.00104.x
Subject(s) - medicine , hemodialysis , coefficient of variation , variation (astronomy) , referral , term (time) , dialysis , nephrology , cardiology , surgery , statistics , mathematics , physics , family medicine , quantum mechanics , astrophysics
During hemodialysis access surveillance, referral for evaluation and correction of stenosis is based upon determination that a significant decrease in blood flow ( Q ) has occurred. However, criteria for determining when a decrease is statistically significant have not yet been established. In this study we established such criteria by analyzing Q variation with the glucose pump test (GPT). We took nine Q measurements in each of 25 patients (18 grafts, 7 fistulas) during three dialysis sessions within a 2‐week period (predialysis and during hours 1 and 3). We determined thresholds that define a significant percentage decrease in Q (Δ Q ) for various p values. In order to confirm the general applicability of these thresholds, we computed the average within‐patient Q variation during the three sessions (computed as a coefficient of variation and referred to as short‐term variation). We then determined the relative influences of biological (true) variation and analytical error on short‐term variation. We found that Δ Q must be > 33% to be significant at p < 0.05, whereas the threshold is > 17% for p < 0.20. Measuring Q at uniform versus different times during the sessions did not significantly reduce these thresholds. We also found that biological variation was nearly as large as short‐term Q variation, whereas analytical error contributed minimally to short‐term variation. In conclusion, this study defines thresholds for a significant Δ Q that have wide application in determining access referral for evaluation and correction of stenosis. Selection of a particular threshold should consider the relative importance of avoiding thrombosis versus avoiding unnecessary procedures. If avoiding unnecessary procedures is a priority, then we recommend a threshold of > 33%. These thresholds apply to other methods of measuring Q , provided analytical error is significantly less than biological variation.