Best Threshold for Diagnosis of Stenosis or Thrombosis within Six Months of Access Flow Measurement in Arteriovenous Fistulae
Bibliographic record
Abstract
Canadian clinical practice guidelines recommend performing angiography when access blood flow (Qa) is <500 ml/min in native vessel arteriovenous fistulae (AVF), but data on the value of Qa that best predicts stenosis are sparse. Because correction of stenosis in AVF improves patency rates, this issue seems worthy of investigation. Receiver-operating characteristic curves were constructed to examine the relationship between different threshold values of Qa and stenosis in 340 patients with AVF. Stenosis was defined by the composite outcome of access failure or angiographic stenosis occurring within 6 mo of the first Qa measurement. The Qa value was then classified as true negative, true positive, false negative, or false positive for stenosis. An additional analysis was performed in which Qa was corrected for systolic BP before assigning it to one of the four diagnostic categories. The area under the curve for the composite definition of stenosis was 0.86. Graphically, Qa thresholds of <500 and <600 ml/min had similar efficacy for detecting stenosis or access failure within 6 mo, and both seemed superior to <400 ml/min. However, the frequency of the composite definition of stenosis among AVF with Qa between 500 and 600 ml/min was only 6 (25%) of 24, as compared with 58 (76%) of 76 when Qa was <500 ml/min. This suggests that most lesions that would be found using a threshold of <600 ml/min occurred in AVF with Qa <500 ml/min and that the small gain in sensitivity associated with the <600-ml/min threshold would be outweighed by the reduced specificity compared with <500 ml/min. Correcting Qa for BP did not improve diagnostic performance or change these results, which were consistent in several sensitivity analyses. Qa measurements seemed to predict stenosis or incipient access failure equally well in groups defined by diabetic status, gender, and AVF location. In conclusion, it was found that Qa <500 ml/min seems to be the most appropriate threshold for performing angiography in patients with native vessel AVF. It is recommended that clinicians arrange angiography when Qa is <500 ml/min in AVF.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.007 | 0.026 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".