Variability in duration of follow up may bias the conclusions of cohort studies of patients with patent foramen ovale
Bibliographic record
Abstract
Closure of patent foramen ovale (PFO) is expected to prevent paradoxical emboli. In the absence of randomized trials, its efficacy has been assessed by comparing uncontrolled cohort studies of medically treated patients with those treated by PFO closure. The objective of this study was to highlight a confounder of such studies, namely, the variability in the duration of follow-up. We searched the literature for cohort studies of patients with ischaemic strokes, including those with PFO. During the first year of follow-up, recurrence hazards in patients younger than 55 years were 1-4% in those with any ischaemic stroke, 1-6% in medically treated patients with PFO and 0-5% in those after PFO closure. In most studies, the recurrence hazards were highest immediately after the index stroke and declined thereafter. Still, hazards were commonly reported in terms of annual averages over a wide range of follow-up periods for the various cohort studies, thereby ignoring the possibility that the duration of the follow-up may in and of itself affect the derived average recurrence hazards. A disregard of the time variance of stroke recurrence may confound the conclusions from comparisons between uncontrolled studies of patients with stroke and PFO.
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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 | 0.055 | 0.146 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.007 | 0.005 |
| Bibliometrics | 0.005 | 0.008 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".