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FLAIR intercomparisons on serum and red cell folate
H van den Berg1, P M Finglas, C Bates
1Dept. of Human Nutrition, TNO Nutrition and Food Research, Zeist, The Netherlands.
Summary
Interlaboratory variation in folate testing was high across multiple methods. Radioassays often overestimate folate due to calibration issues, highlighting the need for better diagnostic kit standardization and reference materials.
Area of Science:
- Clinical Chemistry
- Analytical Chemistry
- Biochemistry
Background:
- Accurate folate measurement is crucial for diagnosing deficiencies and monitoring treatment.
- Significant interlaboratory variability in folate assays has been reported, impacting clinical decisions.
Purpose of the Study:
- To assess interlaboratory variation in serum and red cell folate measurements.
- To identify sources of variability in different folate assay methodologies.
- To emphasize the need for improved standardization in folate diagnostics.
Main Methods:
- Multi-laboratory intercomparison studies using freeze-dried serum, spiked sera, and whole blood control samples.
- Analysis of samples using microbiological, radioassay, HPLC, and chemiluminescence methods.
- Recovery studies with pteroylmonoglutamic acid (PGA) and 5-methyltetrahydrofolic acid (5-MTHF) standards.
Main Results:
- Considerable variability observed between methods (CV 18-41%) and laboratories using similar kits.
- Radioassays showed high PGA (mean 110%) and 5-MTHF (mean 130%) recoveries, suggesting overestimation.
- Whole blood folate measurements exhibited high variability (CV 36-63%).
Conclusions:
- Radioassays tend to overestimate serum folate due to improper standard calibration.
- Assay pH and matrix effects can contribute to measurement variability.
- Improved standardization of diagnostic kits and provision of suitable reference materials are essential for accurate folate determination.