Methodological issues in assessing 25‐hydroxy‐vitamin D levels in newborns
Bibliographic record
Abstract
The accepted biomarker of vitamin D status is 25-hydroxyvitamin D (25(OH)D) however, no gold standard measurement technique is currently recognized. Comparisons between assays are complicated because they use proprietary antibodies which have different affinities for vitamin D metabolites/isoforms. The objective of this study is to try to elucidate this significant health question by comparing two commercially available and routinely utilized assays for measuring 25(OH)D levels in infants. Eighty seven, one month old infants (53 boys) were recruited from the Montreal area during a 2 year period beginning in 2007. A capillary blood was collected by heel prick and analyzed for 25(OH)D using both an enzyme immunoassay (Octeia, IDS Ltd.) and a radioimmunoassay (DiaSorin). Although there was good correlation between methods (r=0.64, p<0.0001), agreement as assessed by Bland Altman method was poor (limits of agreement - 6 to 44%). Infants were categorized according to 25(OH)D levels by both assays (figure 1); the DiaSorin assay classified 98% of infants below the optimal cut-off of 75 nmol/L compared to 53% using the EIA method. Using the cut-off of 50 nmol/L, 52% fell below this level using RIA and 20% with EIA. These assays would result in very different classifications of sufficiency raising important questions regarding the usability/reliability of 25(OH)D assays in small children. Target levels for 25(OH)D are now being set for infants and it is of value to know how well these assays agree. Funded by the Canadian Institutes of Health Research. Figure 1Open in figure viewerPowerPoint Percent of total infants categorized by 25(OH)D level and assay type Grant Funding Source: Canadian Institutes of Health Research
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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 | 0.287 | 0.346 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.002 | 0.004 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.004 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| 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".