Folate blood test
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Understanding Folate Blood Tests: Key Insights and Advances
Folate Deficiency Assessment: Serum and Red Blood Cell Folate
Folate deficiency is commonly assessed through measurements of serum and red blood cell (RBC) folate levels. Serum folate reflects recent dietary intake, while RBC folate indicates long-term folate status in tissues 12. However, there is no consensus on the lower limit of serum folate reference values, complicating the diagnosis of folate deficiency 1. RBC folate is considered more reliable for detecting chronic deficiency due to its stability over approximately four months, as it is fixed during erythropoiesis 6.
New Methods for Folate Measurement: Photon Upconversion Assay
Traditional methods for measuring folate in whole blood face challenges such as high background noise and light absorption. A novel photon upconversion-based homogeneous assay has been developed to address these issues. This method uses resonance energy transfer from upconverting nanophosphor donors to near-infrared fluorescent acceptors, minimizing sample absorption and autofluorescence. This assay offers a simple and fast approach for whole blood folate measurement, with a detection limit of 1 nM and a measurable concentration range of 1.0-100 nM 2.
Dietary Folate Intake and Blood Folate Concentrations
Assessing dietary folate intake through traditional methods is complex and often inaccurate. Validation studies have shown that correlations between dietary folate intake and blood folate concentrations vary from weak to moderate. These correlations improve when dietary supplements are considered and when serum/plasma folate is used as the biomarker instead of RBC folate 3. This highlights the importance of using updated food composition databases and considering dietary supplements in dietary assessments.
Folate and Vitamin B12 Deficiency: Laboratory Indicators
Folate and vitamin B12 deficiencies are significant global health issues. Laboratory tests for these deficiencies include measurements of serum/plasma folate, RBC folate, and surrogate biochemical markers like plasma homocysteine. Each test has limitations, and no single test can achieve perfect sensitivity or specificity. Therefore, a combination of tests is often used to establish nutritional status and monitor the efficacy of interventions 4.
Genetic Factors: MTHFR Polymorphism and Blood Folate Levels
The methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism affects folate metabolism and is associated with lower blood folate concentrations. Studies have shown a consistent pattern of lower serum/plasma and RBC folate levels in individuals with the TT genotype compared to those with the CC genotype. This genetic variation has implications for the risk of neural tube defects and highlights the need for personalized approaches in folate supplementation 5.
Reducing Unnecessary Folate Testing
Efforts to reduce unnecessary RBC folate testing have shown significant success. Restricting the ability to order RBC folate tests to specific clinicians in gastroenterology and hematology led to a 94.4% reduction in testing, resulting in substantial cost savings without negatively impacting clinical outcomes 7. Additionally, data from Canadian hospitals indicate that folate deficiency in inpatients is rare, suggesting that routine folate testing in this population may be unnecessary 8.
Advanced Analytical Techniques: LC-MS/MS
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a powerful tool for measuring various forms of folate and folate catabolites in serum. This method offers high sensitivity and specificity, allowing for the accurate assessment of folate status in clinical and epidemiological studies. It can measure multiple folate species and catabolites, providing a comprehensive picture of folate metabolism 910.
Conclusion
Folate blood tests are essential for diagnosing folate deficiency and monitoring folate status. Advances in measurement techniques, such as photon upconversion assays and LC-MS/MS, have improved the accuracy and reliability of these tests. Understanding the relationship between dietary intake, genetic factors, and blood folate levels is crucial for effective diagnosis and intervention. Reducing unnecessary testing can lead to significant cost savings without compromising patient care.
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Most relevant research papers on this topic
Serum and red blood cell folate testing for folate deficiency: new features?
Serum folate cut-off values should be based on the relationship between serum and red blood cell folate, vitamin B12, and homocysteine, rather than solely on serum folate levels.
Observational Study
Rigorous JournalHomogeneous assay for whole blood folate using photon upconversion.
The new photon upconversion-based method provides a simple and fast method for whole blood folate measurement, with good correlation to competitive heterogeneous assays.
In Vitro StudyDietary intake and biological measurement of folate: a qualitative review of validation studies.
Validating dietary folate intake instruments against circulating concentration biomarkers requires careful attention to methodological issues, including seasonality, updated food composition databases, and considering fortified foods and supplements.
Systematic ReviewRigorous JournalIndicators for assessing folate and vitamin B-12 status and for monitoring the efficacy of intervention strategies.
Laboratory tests are essential for assessing folate and vitamin B-12 status and monitoring the efficacy of interventions, but current tests have limitations.
Very Rigorous Journal
Highly CitedAssessing the association between the methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism and blood folate concentrations: a systematic review and meta-analysis of trials and observational studies.
MTHFR C677T genotypes are associated with lower blood folate concentrations, potentially impacting the population-level risk of neural tube defects.
Meta-AnalysisVery Rigorous JournalHighly CitedLaboratory assessment of folate (vitamin B9) status
Folate deficiency can lead to megaloblastic anaemia, neural tube defects, cognitive decline, depression, and neuropathy, and excessive exposure to folic acid can cause adverse health effects.
Highly CitedReduction in Unnecessary Red Blood Cell Folate Testing by Restricting Computerized Physician Order Entry in the Electronic Health Record.
Restricting RBC folate ordering in the electronic health record led to a large and sustained reduction in unnecessary testing, resulting in significant cost savings without significantly impacting folate deficiency diagnosis.
Observational StudyFolate testing in hospital inpatients.
Folate deficiency in hospital inpatients is nearly nonexistent, and significant savings could be achieved by eliminating folate testing on inpatients.
Observational StudyMeasurement of folates in serum and conventionally prepared whole blood lysates: application of an automated 96-well plate isotope-dilution tandem mass spectrometry method.
This automated 96-well plate LC/MS/MS method accurately measures intact folate monoglutamates in whole blood lysates and serum, improving sample throughput and reducing manual sample preparation.
Highly CitedLiquid chromatography-tandem mass spectrometry analysis of folate and folate catabolites in human serum.
This method accurately measures various folate species and 2 folate catabolites in human serum, aiding in the assessment of folate status in clinical settings and epidemiological studies.
Highly Cited