The loss of 5-methyltetrahydrofolate in human serum under suboptimal preanalytical conditions can only partially be recovered by an oxidation product1,2,3

Details

• Alternative Title:
  J Nutr
• Personal Author:
  Fazili, Zia ; Sternberg, Maya R. ; Paladugula, Neelima ; Whitehead, Ralph D. ; Chen, Huiping ; Pfeiffer, Christine M.
• Description:
  Background ; Maintaining folate stability during sample handling is important, yet challenging. ; Objective ; We investigated the effects of suboptimal preanalytical conditions on serum folate stability. ; Design ; Using an HPLC-tandem MS method we measured folates 5-methyltetrahydrofolate (5-methylTHF), folic acid, and MeFox (5-methylTHF oxidation product), minor forms at or below limit of detection in human serum exposed to suboptimal conditions. ; Results ; Whole blood samples (n = 21) stored at 32°C for ≤3 d (experiment 1 – delayed processing) showed significant decreases in serum total folate (tFOL; sum of folate forms) 11–32%, 5.5–15.9 nmol/L and 5-methylTHF (36–62%, 14.5–25.1 nmol/L) and a significant increase in MeFox (346–415%, 7.17–8.63 nmol/L). Serum samples (n = 21) stored at 11°C for 7–14 d (experiment 2 – delayed freezing) also showed significant decreases in tFOL (4.6–10.4%, 2.3–5.1 nmol/L) and 5-methylTHF (8.4–29%, 3.4–11.6 nmol/L) and significant increases in MeFox (88–320%, 1.82–6.62 nmol/L). The molar loss in 5-methylTHF exceeded the gain in MeFox in these 2 experiments. When we exposed 3 serum pools (tFOL 16.7–58.3 nmol/L) for 24 h to 37°C elevated temperature (experiment 3), the significant decrease in 5-methylTHF (33% on average) was compensated by an equimolar gain in MeFox. Repeated freeze/thawing (≤3 cycles) of serum closed (experiment 4) and open (experiment 5) vials showed generally stable folates with small (<1 nmol/L) changes. Long-term (≤12 mo) exposure of 3 serum pools (tFOL 17.5–63.7 nmol/L) to suboptimal (−20°C) freezing temperature (experiment 6) showed significant decreases in tFOL (5% on average) already after 3 mo. The molar loss in 5-methylTHF exceeded the gain in MeFox. Folic acid generally showed good stability. ; Conclusions ; To avoid folate losses, unprocessed whole blood should be protected from elevated temperature and serum should not be refrigerated for >2 d or long-term stored at −20°C.
• Subjects:
  • Article
  • Folate
  • MeFox
  • stability
  • degradation
  • preanalytical
  • delayed processing
  • frozen storage
  • freeze/thawing
  • and HPLC-MS/MS
  More +
• Source:
  J Nutr. 144(11):1873-1879.
• Pubmed ID:
  25332487
• Pubmed Central ID:
  PMC5332148
• Document Type:
  Journal Article
• Funding:
  CC999999/Intramural CDC HHS/United States
• Volume:
  144
• Issue:
  11
• Download URL:
  https://stacks.cdc.gov/view/cdc/44466/cdc_44466_DS1.pdf
• File Type:
  [PDF - 518.30 KB]
• Collection(s):
  CDC Public Access
• Main Document Checksum:
  urn:sha256:bf00cbc140fc11b3a30d514f0e0160cddcfaef738bb9056b63d6835b54d7d9d7