Conversion between B-type natriuretic peptide and N-terminal pro B-type natriuretic peptide in perioperative risk assessment: protocol for a prospective cohort study
Bibliographic record
Abstract
INTRODUCTION: Both B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-pro-BNP) are used to identify patients at risk of perioperative vascular events, but prognostic thresholds have been established in a large prospective cohort for NT-pro-BNP only. We designed this study to inform perioperative risk interpretation of BNP values. Our primary objective is to validate a formula to convert BNP to NT-pro-BNP concentrations before non-cardiac surgery. The secondary objective is to determine the association between BNP categories (established based on conversion from NT-pro-BNP categories) and a composite outcome of myocardial injury after non-cardiac surgery (MINS) and vascular death. METHODS AND ANALYSIS: This is a single-centre, prospective cohort study in patients undergoing non-cardiac surgery who are >65 years old, Revised Cardiac Risk Index ≥1 or >45 years old with significant cardiovascular disease. BNP and NT-pro-BNP will be measured preoperatively, and troponin measurements will be analysed on postoperative days 1, 2 and 3. MINS and vascular death will be ascertained up to 30 days after surgery. The primary analyses will compare measured NT-pro-BNP values to those predicted by an existing formula (from a non-surgical population) based on BNP concentrations and patient characteristics, and recalibrate and update the formula with additional variables. Secondary analyses will estimate the relationship between categories of measured BNP (corresponding to established NT-pro-BNP thresholds) and the composite of MINS and vascular death. The target sample size of 431 patients is based on our primary analysis (assessing the conversion formula). ETHICS AND DISSEMINATION: Ethics approval has been obtained by the Queen's University Health Sciences Research Ethics Board, and all participants will provide informed consent for participation in the study. The results will be submitted for publication in conferences and in a peer-reviewed journal, and will inform perioperative vascular risk interpretation of preoperative BNP. TRIAL REGISTRATION NUMBER: NCT05352698.
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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 | 0.070 | 0.045 |
| Meta-epidemiology (narrow) | 0.004 | 0.003 |
| Meta-epidemiology (broad) | 0.006 | 0.006 |
| Bibliometrics | 0.003 | 0.005 |
| Science and technology studies | 0.004 | 0.002 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.004 | 0.003 |
| Research integrity | 0.004 | 0.005 |
| Insufficient payload (model declined to judge) | 0.022 | 0.008 |
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".