45: Determining the Agreement Between Commonly Used Assays to Measure 25-Hydroxyvitamin D in Young Children
Bibliographic record
Abstract
Determining vitamin D deficiency or insufficiency as defined by the Canadian Paediatric Society (CPS) is accomplished through measuring serum levels of 25-hydroxyvitamin D. Variation in 25-hydroxyvitamin D measurement may lead to misdiagnosis. Several different 25-hydroxyvitamin D assays are used in clinical practice but the comparability of these assays is unclear. The primary objective was to examine the agreement in 25-hydroxyvitamin D concentration measured by three different assays on the same serum sample: Diasorian Liason® (DL), Tandem Mass Spectrometry (MS) and Roche electrochemiluminescence (ECL). Serum samples from a cohort of children under 5 years of age were included in this study. 25-hydroxyvitmain D concentration was measured using DL, MS and ECL at two laboratories. Agreement between assays was explored using Spearman correlations and Bland-Altman plots. CPS endorsed 25-hydroxyvitamin D cut-points, 50 nmol/L and 75 nmol/L, were used to compare differences in classification of vitamin D status. In addition, clinical predictors of 25-hydroxyvitamin D, such as cow's milk intake and vitamin D supplementation, were modeled using three separate multivariate linear regression models with 25-hydroxyvitamin D for each assay as the outcome. The r-squared was compared between models to determine the variation in vitamin D predictors accounted for by each 25-hydroxyvitamin D assay. 264 participants were included in this study. Mean age was 43 months, 56% were male, 64% were European, and mean zBMI was 0.26. The percentages of children falling below each cut-point (50 and 75 nmol/L) were respectively: 7% and 44% for DL; 4% and 35% for MS; and 9% and 36% for ECL. The spearman correlation coefficient was 0.46 for DL and MS, 0.65 for MS and ECL and 0.55 for DL and ECL. The three assays appeared to have poor agreement on Bland Altman plots: DL and MS mean difference was 6.5 (STD 28); MS and ECL mean difference was 1.7 (STD 25); and DL and ECL mean difference was −4.7 (STD 26). The variability in vitamin D clinical predictors explained by each assay was 8.6% using DL, 7.5% using ECL and 1.4% using MS. It appears that there is relatively poor agreement between all three assays commonly used for 25-hydroxyvitamin D measurement. DL and ECL explain more of the variability in vitamin D predictors. More consideration needs to be given to the accuracy of 25-hydroxyvitamin D measurement in children.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.028 | 0.027 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".