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Folate assays: serum or red cell?
K Phekoo1, Y Williams, S A Schey
1Guy's and St Thomas' Trust, London.
Summary
Serum folate assays are recommended as the most appropriate screening test for folate deficiency, often alongside vitamin B12 testing. This audit analyzed folate testing practices across multiple centers to guide laboratory recommendations.
Area of Science:
- Clinical Chemistry
- Hematology
- Laboratory Medicine
Background:
- Folate and vitamin B12 deficiency testing is common across various medical specialties.
- Significant variability exists in folate assay methodologies, request numbers, and reference ranges among different centers.
Purpose of the Study:
- To audit folate assay methodologies and analyze indications for testing.
- To determine the most appropriate folate assay for laboratory use.
Main Methods:
- A questionnaire-based audit involving 30 centers (24% participation).
- Analysis of 1,259 consecutive folate assay requests from a single laboratory.
- Correlation analysis of serum and red cell folate levels.
Main Results:
- Significant correlation found between serum and red cell folate levels (r = 0.49).
- No correlation between serum and red cell folate in non-macrocytic patients with low serum folate.
- Hematological abnormalities were the primary indication, but 36% of requests were for non-specific reasons.
Conclusions:
- Serum folate assay is the most appropriate screening test for folate deficiency.
- Serum folate testing can be effectively combined with vitamin B12 assays.
- Standardization of folate assay methods and clearer indications for testing are needed.