Performance of a universally offered prenatal screening program incorporating cfDNA in Ontario, Canada: a descriptive population-based cohort study of 280,000 pregnancies
Bibliographic record
Abstract
A bstract Objectives To measure the population-based performance and impact of Ontario, Canada’s modified-contingent prenatal screening system for the detection of trisomies 21 (T21) and 18 (T18). Design A retrospective, descriptive cohort study examining routinely collected data from BORN Ontario, which captures linkable population data for prenatal and neonatal health encounters across a variety of settings (e.g., laboratories, birthing hospitals and midwifery practice groups). Setting A province-wide and publicly funded prenatal screening program in Ontario, Canada offering cfDNA screening for those at increased risk of having a pregnancy with T21 or T18. Participants 373,682 singleton pregnancies with an estimated due date between September 1 2016 and March 31, 2019 who were offered publicly funded prenatal screening. Main outcome measures Prenatal detection of T21 or T18, ascertained by cytogenetic results. Performance was assessed by calculating sensitivity, specificity, positive predictive value and negative predictive value against confirmatory diagnostic cytogenetic results and birth outcomes. The secondary objective was to determine the impact of contingent cfDNA screening by measuring uptake and the proportion of T21 screen-positive pregnancies undergoing subsequent cfDNA screening and invasive prenatal diagnostic testing (PND). Results 69% of pregnancies in Ontario underwent prenatal screening for T21/T18. The modified-contingent screen sensitivity was 89.9% for T21 and 80.5% for T18. The modified-contingent screen-positive rate was 1.6% for T21 and 0.2% for T18. The cfDNA screening test failure rate was 2.2% (final result including multiple attempts). The PND rate among pregnancies screened was 2.4%. Conclusions This study is the largest evaluation of population-based performance of a publicly funded cfDNA prenatal screening system. We demonstrated a robust screening system with high sensitivity and low PND consistent with smaller validation studies
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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 | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.003 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.002 | 0.001 |
| 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".