Competitive chemiluminescent enzyme immunoassay for vitamin B12 analysis in human milk.
Recent discoveries of matrix interferences by haptocorrin (HC) in human milk and serum show that past analyses of vitamin B12 in samples with high HC content might have been inaccurate (Lildballe et al., 2009; Carmel & Agrawal, 2012). We evaluated two competitive enzyme-binding immunoassays for serum/plasma (IMMULITE and SimulTRAC-SNB) for B12 analysis in human milk. B12-recovery rates (United States Environmental Protection Agency, 2007) were determined to be 78.9 ± 9.1% with IMMULITE and 225 ± 108% (range 116-553%) using SimulTRAC-SNB, most likely due to the presence of excess HC. HC-interferences were not observed with the IMMULITE assay, rendering previously reported mandatory HC-removal (Lildballe et al., 2009) unnecessary. Linearity continued at low B12-concentrations (24-193 pM; r(2)>0.985). Milk B12 concentrations from Bangladeshi women (72-959 pM) were significantly lower than those from California (154-933 pM; p<0.0001) showing IMMULITE's robustness against the complex milk matrix and its ability to measure low milk B12 concentrations.
USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA; Department of Nutrition, University of California, One Shields Ave., Davis, CA 95616, USA. Electronic address: daniela.hampel@ars.usda.gov.
Daniela
D
Hampel
USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA.
Setareh
S
Shahab-Ferdows
USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA.
Joseph M
JM
Domek
USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA; Department of Nutrition, University of California, One Shields Ave., Davis, CA 95616, USA; International Centre for Diarrheal Disease Research, Dhaka, Bangladesh.
Towfida
T
Siddiqua
International Centre for Diarrheal Disease Research, Dhaka, Bangladesh.
Rubhana
R
Raqib
USDA, ARS Western Human Nutrition Research Center, 430 W. Health Sciences Drive, Davis, CA 95616, USA; Department of Nutrition, University of California, One Shields Ave., Davis, CA 95616, USA.
Lindsay H
LH
Allen
D000328:Adult; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D008163:Luminescent Measurements / Q000379:methods*; D008895:Milk, Human / Q000737:chemistry*; D014805:Vitamin B 12 / Q000032:analysis*
D014805:Vitamin B 12
Chemiluminescence; Cobalamin; Haptocorrin; Human milk; Radioassay; Vitamin B12