The loss of 5-methyltetrahydrofolate in human serum under suboptimal preanalytical conditions can only partially be recovered by an oxidation product1,2,3
Published Date:Sep 17 2014
Source:J Nutr. 144(11):1873-1879.
Blood Specimen Collection
Chromatography, High Pressure Liquid
Limit Of Detection
Sensitivity And Specificity
Tandem Mass Spectrometry
Pubmed Central ID:PMC5332148
Funding:CC999999/Intramural CDC HHS/United States
Maintaining folate stability during sample handling is important, yet challenging.
We investigated the effects of suboptimal preanalytical conditions on serum folate stability.
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.
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.
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.
application/pdf application/octet-stream image/gif image/jpeg
You May Also Like: