A-356 Development of postpartum-specific reference intervals for serum vitamin B12 and holotranscobalamin for reliable assessment of vitamin B12 status
Year: 2025
Type: conference-abstract
Abstract: Background Maternal vitamin B12 levels fluctuate during pregnancy and postpartum due to dynamic changes in holotranscobalamin and holohaptocorrin driven by physiochemical shifts. Total B-12 does not reliably indicate active B-12 adequacy for cellular metabolism. Additionally, postpartum holoTC variations with total B-12 necessitate further exploration, as recent research questions Herbert*s B-12 deficiency model. Current total B-12 and holoTC cutoffs for the non-pregnant population may not be applicable to postpartum women, as breastfeeding, nutrition, and hormonal factors remain distinct. This could lead to misclassifying their B-12 status as insufficient or deficient. Therefore, the aim of this study is to evaluate and establish specific reference intervals for total B-12 and holoTC in postpartum women, as no previous studies, to the best of our knowledge, have explored this possibility. Methods This study included 427 women at 6 weeks postpartum who had a normal vaginal delivery with no postpartum feto-maternal complications. Females with a history of hepatic/renal disease, a strict vegetarian diet, or B12 supplementation were excluded. Serum total vitamin B12, holotranscobalamin (holoTC), methylmalonic acid (MMA), homocysteine (HCY), and 5-methyl tetrahydrofolate (5-methylTHF) were measured using commercially available ELISA kits. Reference intervals for serum total B-12 and holoTC concentrations were determined in accordance with the CLSI EP28-A3c guidelines. Medcalc version 23.1.6 was used to calculate the central 95% reference limits by parametric approach for total B-12 reference values after log transformation. A non-parametric approach was applied to estimate the reference limits for holoTC reference values. Results Using the existing total B-12 cutoffs for the non-pregnant population (<148 pmol/L = deficient; <194 pmol/L = insufficient), 23 of 427 postpartum women (5.4%) were classified as deficient, while 91 (21.3%) had insufficient B12 levels. Women with insufficient total B12 levels exhibited significantly higher holoTC levels than those with sufficient B12 levels (p < 0.05). There was no significant difference in the levels of 5-methylTHF, homocysteine and methylmalonic acid between the two groups. Based on the CLSI EP28-A3c guidelines, the central 95% reference interval for total B12 was determined to be 133 – 428pmol/L (90% CI for Lower Reference Limit: 127 – 138 pmol/L; 90% CI for Upper Reference Limit: 411 – 446 pmol/L). The reference interval for holoTC was found to be 24.5 – 158.4pmol/L (90% CI for Lower Reference Limit: 18.4 – 29.4 pmol/L; 90% CI for Upper Reference Limit: 151.0 – 172.8 pmol/L). With the new reference interval, 11 out of 427 postpartum women (2.6%) were deficient in total B-12 levels. Conclusion The existing total B-12 cutoffs falsely overestimate deficiency and insufficiency in postpartum women, as evidenced by normal levels of 5-methylTHF, homocysteine, and MMA. The elevated holoTC levels in women with insufficient total B-12 suggest that physiochemical changes during pregnancy and postpartum may have influenced holoTC dynamics to sustain cellular metabolism. This study led to the development of novel postpartum-specific reference intervals for total B-12 and holoTC, resulting in a significantly lower number of women classified as deficient. Future research should validate these postpartum-specific reference limits and determine a threshold for subclinical B12 deficiency.
Source: Clinical Chemistry
Authors: Soundravally Rajendiran, Devanatha Desikan, Pooja Dhiman, P Veena, Balaji Bharadwaj, Nancy Premkumar
Language: English
Subfield: Rheumatology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W4414741052
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