Analytic validation of commercially available immunoassays for the measurement of serum cobalamin and folate concentrations in pigs.

BACKGROUND: Cobalamin (vitamin B12 ) and folate (vitamin B9 ) are important for the amino acid metabolism and nucleic acid synthesis. Immunoassays for the measurement of both vitamins in serum are routinely used in people, cats, and dogs, serving as indicators for clinical disorders including cobalamin and/or folate deficiency, small intestinal dysbiosis, or inadequate dietary supply of these vitamins. The analysis of these analytes may also be clinically useful in pigs. OBJECTIVE: The purpose of this study was to analytically validate immunoassays for the measurement of cobalamin and folate concentrations in porcine serum, and to determine serum cobalamin and folate concentrations in healthy newborn pigs pre- and postweaning. METHODS: Assay validation for both vitamins included the determination of linearity, accuracy, and intra- and inter-assay variability using serum samples from 10 pigs. Also, serum cobalamin and folate concentrations were compared in piglets between pre- and postweaning. RESULTS: For both vitamins, observed-to-expected ratios for linearity and accuracy were 93.2 ± 14.3% and 100.3 ± 8.1% (mean ± standard deviation), respectively. Intra- and inter-assay coefficients of variation for serum were ≤ 8.7% and ≤12.5%, respectively. Significantly higher serum cobalamin and lower folate concentrations were observed in piglets at the time of weaning than at postweaning (P < .0061; P < .0001, respectively). CONCLUSIONS: Both immunoassays are linear, accurate, precise, and reproducible for measurement of porcine serum cobalamin and folate concentrations. Piglets differing in age by only 12 days had significantly different serum cobalamin and folate concentrations. The implications of differing serum cobalamin and folate concentrations in pigs at different stages of life should be further investigated.

Serum folate, cobalamin, homocysteine and methylmalonic acid concentrations in pigs with acute, chronic or subclinical Lawsonia intracellularis infection.

Lawsonia intracellularis is the causative agent of porcine proliferative enteropathy. The clinical presentation can be acute (i.e. proliferative hemorrhagic enteropathy, PHE), chronic (i.e. porcine intestinal adenomatosis, PIA) or subclinical. In humans with chronic enteropathies, low serum folate (vitamin B(9)) and cobalamin (vitamin B(12)) concentrations have been associated with increased serum concentrations of homocysteine and methylmalonic acid (MMA), which reflect the availability of both vitamins at the cellular level. The aim of this study was to evaluate serum folate, cobalamin, homocysteine and MMA concentrations in serum samples from pigs with PHE, PIA or subclinical L. intracellularis infection, and in negative controls. Serum folate, cobalamin, homocysteine and MMA concentrations differed significantly among pigs in the PHE, PIA, subclinical and negative control groups. Serum folate concentrations in the PHE and PIA groups were lower than in the subclinical and negative control groups, while serum cobalamin concentrations were lower in the PIA group than in other groups. Serum concentrations of homocysteine were higher in the PHE, PIA and subclinical groups than in the negative control group. Serum concentrations of MMA were higher in the subclinical and PIA groups than in the control group. These data suggest that pigs infected with L. intracellularis have altered serum cobalamin, folate, homocysteine and MMA concentrations.