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Two international Round Robin studies showed good comparability of 5-methyltetrahydrofolate, but poor comparability of folic acid measured in serum by different HPLC-MS/MS methods

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  • English
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    Details:

    • Alternative Title:
      J Nutr
    • Personal Author:
    • Description:
      Background

      Serum folate methods produce different results. The comparability of HPLC-MS/MS methods is not well-documented.

      Objective

      We conducted an international “Round Robin” investigation to assess the comparability, precision, and accuracy of serum folate HPLC-MS/MS methods.

      Design

      The CDC laboratory, 7 laboratories with independently-developed methods (group 1), and 6 laboratories with an adapted CDC method (group 2) analyzed folate forms in 6 serum pools and 6 calibrators from CDC (duplicate analysis over 2 days) and in 2 three-level reference materials (duplicate analysis).

      Results

      All laboratories measured 5-methyltetrahydrofolate (5-methylTHF) and folic acid; some measured additional folate forms. Geometric mean concentrations (nmol/L) for 5-methylTHF in the 6 serum pools were 18.3 (CDC), 13.8–28.9 (group 1), and 16.8–18.6 (group 2); for folic acid, 3.42 (CDC), 1.09–4.74 (group 1), and 1.74–2.90 (group 2). The median imprecision (CV) for 5-methylTHF was 4.1% (CDC), 4.6%–11% (group 1), and 1.7%–6.0% (group 2); for folic acid, 6.9% (CDC), 4.9%–20% (group 1), and 3.9%–23% (group 2). The mean (SD; range) recovery of 5-methylTHF spiked into serum was 98% (27%; 59%–138%) for group 1 and 98% (10%; 82%–111%) for group 2; for folic acid, 93% (29%; 67%–198%) for group 1 and 81% (16%; 64%–102%) for group 2. The mean relative bias for 5-methylTHF compared to the reference material certificate value was 12% (CDC), -24% to 30% (group 1), and -0.6% to 16% (group 2); for folic acid, 73% (CDC), -47% to 578% (group 1), and -3.3% to 67% (group 2).

      Conclusions

      For 5-methylTHF, group 2 laboratories demonstrated better agreement and precision, less variable spiking recovery, and less bias using a reference material. Laboratory performance for folic acid was highly variable and needs improvement. Certified reference materials for serum folate forms and total folate are needed to improve method accuracy.

    • Subjects:
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    • Source:
      J Nutr. 147(9):1815-1825
    • Pubmed ID:
      28768831
    • Pubmed Central ID:
      PMC5712443
    • Document Type:
      Journal Article
    • Funding:
      CC999999/Intramural CDC HHSUnited States/
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