Prospective Evaluation of Accelerate Pheno™ System (AXDX) Version 1.1 for Reducing Turn-Around-Time (TAT) in Identification/Antimicrobial Susceptibility Testing (ID/AST) of Gram-Negative Bacilli (GNB) from Positive Blood Cultures (+BC) using AXDX PhenoTest™ BC Kits
Bibliographic record
Abstract
This study evaluated AXDX (uses FISH/real-time microscopy to obtain ID/AST direct from +BC in <7h) for accuracy against reference mass spectrometry (MS, VITEK® MS, bioMérieux) and broth microdilution (BMD), respectively. AXDX TAT was timed against current reporting for ID using MS and VITEK®2 (VT2, bioMérieux) for AST (VT2 data not presented). Blood from 173 semi-consecutive +BC tested in BacT/Alert® (bioMérieux) with GNB on Gram were tested in AXDX. Susceptible/intermediate/resistant (S/I/R) interpretations were as per CLSI-M100-S27 for cefazolin (CFZ), ceftriaxone (CRO), ceftazidime (CAZ), piperacillin/tazobactam (TZP), ertapenem (ETP), meropenem (MEM), ciprofloxacin (CIP), gentamicin (GM), tobramycin (TOB), and amikacin (AN). ID and AST results were combined across GNB-genera for assessment as per Cumitech 31A for ≥90% agreements [identificatoin, essential (EA); categorical (CA)] and errors [very major (VME) <3%; combined major/minor (ME/mE) <7%]. 142 (82.1%) AXDX results were evaluable (ID-agreed/AST-reported) for 78 Escherichia coli, 27 Klebsiella species, 17 Pseudomonas aeruginosa, 5 Enterobacter cloacae, 8 Serratia marcescens, 3 Proteus mirabilis, 2 Acinetobacter baumannii and 2 Citrobacter freundii as seen tabulated below. Limits were exceeded for underlined values but 95% confidence intervals (CI) overlapped acceptable limits except in values marked with asterisks [EA (CAZ: 68.7–82.7), ME/mE (CFZ: 5.1–16.8; CAZ: 10–21.9; TZP: 9.2–20.8)]. VME were not evaluable (NE) for TZP, ETP, MEM, or AN due to insufficient numbers of GNB resistant to these agents. ID/AST TAT means (ranges) for AXDX were 1:21h (1:19–1:24h)/6:38h (6:30–6:59h) conmpared to MS/VT2 of 8:49h (2:49–76:48h)/38:23h (19:44–64:22h), respectively; paired t-tests, P < 0.0001/P < 0.0001; difference of means: 8:17h (95% CI:6:55–9:38h)/28:41h (95% CI:26:53–30:29h)]. These data suggest AXDX will significantly reduce ID/AST TAT in GNB bacteremia (ID: 8:49h to 1:21h; AST: 38:23h to 6:38h) with potential to significantly improve patient outcomes. Acceptable accuracy was achieved for ID and AST for most agents. A limitation was the lack of GNB causing bacteremia with resistance to AN, TZP, ETP or MEM in during evaluation. B. M. Willey, Mount Sinai Hospital: Investigator, Educational support S. M. Poutanen, Accelerate Diagnostics: Research Contractor and Scientific Advisor, Consulting fee and Research support
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".