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Red cell or serum folate: what to do in clinical practice?
Christopher-John L Farrell1, Susanne H Kirsch, Markus Herrmann
1Laverty Pathology, North Ryde, NSW, Australia.
Clinical Chemistry and Laboratory Medicine
|March 2, 2013
Summary
Serum folate testing is a more reliable and cost-effective method for assessing folate status compared to red cell folate. Serum folate assays show fewer analytical variations and better correlation with deficiency markers.
Area of Science:
- Clinical Biochemistry
- Nutritional Science
- Laboratory Medicine
Background:
- Folate deficiency is associated with various clinical issues, necessitating accurate folate status assessment.
- The optimal laboratory test for routine folate status evaluation remains unclear.
- Both serum and red cell folate assays are available, but red cell folate is more time-consuming and expensive.
Purpose of the Study:
- To compare the performance characteristics of serum folate and red cell folate assays.
- To determine if the advantages of red cell folate testing justify its increased cost and time.
- To evaluate the reliability of each assay in assessing folate status and response to supplementation.
Main Methods:
- Literature review comparing serum and red cell folate assay performance.
- Analysis of factors influencing assay variability, including sample pre-treatment and hematocrit.
- Evaluation of assay correlation with homocysteine, a marker of folate deficiency.
- Assessment of assay response to folic acid supplementation and impact of MTHFR polymorphism.
Main Results:
- Red cell folate assays exhibited analytical variability linked to sample pre-treatment, oxygen saturation, and hematocrit.
- Neither assay was definitively superior in characterizing deficiency, but serum folate correlated better with homocysteine.
- Both assays responded to folic acid supplementation, with serum folate showing a greater response and dose-dependency.
- The C677T polymorphism of methylenetetrahydrofolate reductase can increase analytical variability in red cell folate assays.
Conclusions:
- Serum folate testing is generally superior to red cell folate testing due to lower cost, faster turnaround time, and fewer analytical variables.
- Serum folate assays may provide a more accurate assessment of folate status and response to supplementation.
- Further research may be needed to fully elucidate the clinical utility of each assay in specific populations.
