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Methodological issues in assessing 25‐hydroxy‐vitamin D levels in newborns
Author(s) -
Gallo Sina,
Agellon Sherry,
Vanstone Catherine A,
Weiler Hope A,
Rodd Celia
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.537.1
Subject(s) - vitamin d and neurology , medicine , radioimmunoassay , biomarker , immunoassay , vitamin d binding protein , limits of agreement , heel , pediatrics , antibody , chemistry , immunology , biochemistry , nuclear medicine , anatomy
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. 1Percent of total infants categorized by 25(OH)D level and assay typeGrant Funding Source : Canadian Institutes of Health Research