Development and Validation of a New Low-Cost Enzyme-Linked Immunoassay for Serum and Dried Blood Spot XXXX .

@entity1 @entity1496 @entity5377 @entity3745
BACKGROUND: @entity3745 (Tg), a biomarker of @entity1496 nutrition, can be measured on dried blood spots (DBS), which simplifies collection and transport in surveys. The World Health Organization recommends DBS-Tg for monitoring @entity1496 status in @entity1 . It could also be a useful @entity1496 biomarker during pregnancy. However, the Tg antibody (Ab) used in earlier DBS-Tg assays is no longer commercially available. The aims of the present study were: (i) to develop a new low-cost serum and DBS-Tg sandwich enzyme-linked immunosorbent assay for assessment of Tg in population studies; (ii) to check the stability of DBS-Tg during long-term storage; and (iii) to assess within-subject variability in DBS-Tg. METHODS: Serum and DBS samples were measured from healthy pregnant @entity1 (n   =   424) with the new assays, as well as the Immulite 2000 ( @entity5377 ), including TgAb positive (n   =   150) and TgAb negative (n   =   274) @entity1 . DBS-Tg stability was tested over 15 weeks of storage at -20  C. Within-subject variability was evaluated over four weeks in four healthy adults. RESULTS: Intra-assay and interassay variability was 4.4-7.3% and 10.1-12.9% for the new serum Tg assay, and 7.6-12.3% and 7.6-16.5% for the DBS-Tg assay. Correlation between the two serum methods was high (r   =   0.68, p   <   0.01). Assay performance in all @entity1 and those TgAb negative was comparable. Correlation between the new serum Tg assay and the DBS-Tg assay was high (r   =   0.78, p   <   0.01), and agreement expressed as a function of the average Tg concentration for the two methods (X) was 0.59X   -4.59    g/L. DBS-Tg was stable for 15 weeks stored at -20  C. Within-subject variability in DBS-Tg was 21.1%. Reagents and antibodies costs for the new serum and DBS assays are    US 1. CONCLUSIONS: These new low-cost serum and DBS-Tg assays perform well over a wide range of Tg concentrations, and the field-friendly DBS assay may be particularly useful in population studies of @entity1496 nutrition.
