Folate (Folic Acid)

CPT: 82746
Print Share

Test Details

Use

Detect folate deficiency; monitor therapy with folate; evaluate megaloblastic and macrocytic anemia; evaluate alcoholic patients and those with prior jejunoileal bypass for morbid obesity or those with intestinal blind-loop syndrome

Limitations

Folate assays of samples from patients receiving therapy with certain pharmaceuticals (eg, methotrexate or leucovorin), are contraindicated because of the cross-reactivity of folate-binding protein with these compounds.1 Serum samples should not be altered with additives (biocides, antioxidants, or substances possibly changing the pH of the sample) in order to avoid erroneous folate recovery.

Hemolysis may significantly increase folate values due to high concentrations of folate in red blood cells; therefore, hemolyzed samples are not suitable for this assay.1

Samples with extremely high total protein concentrations (eg, patients suffering from Waldenström macroglobulinemia) are not suitable for use in this assay, since they may lead to the formation of protein gel in the assay cup.1

As with all tests containing monoclonal mouse antibodies, erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or have received them for diagnostic purposes.1 In rare cases, interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur.1 The test contains additives that minimize these effects.

Methodology

Electrochemiluminescence immunoassay (ECLIA)

Reference Interval

>3.0 ng/mL

Additional Information

Folates are compounds of pteroylglutamic acid (PGA) that function as coenzymes in metabolic reactions involving the transfer of single-carbon units from a donor to a recipient compound. Folate, with vitamin B12, is essential for DNA synthesis, which is required for normal red blood cell maturation.2 Humans obtain folate from dietary sources including fruits, green and leafy vegetables, yeast, and organ meats.3 Folate is absorbed through the small intestine and stored in the liver.

Low folate intake, malabsorption as a result of gastrointestinal diseases, pregnancy, and drugs such as phenytoin are causes of folate deficiency.4 Folate deficiency is also associated with chronic alcoholism.5 Folate and vitamin B12 deficiency impair DNA synthesis, causing macrocytic anemias. These anemias are characterized by abnormal maturation of red blood cell precursors in the bone marrow, the presence of megaloblasts, and decreased red blood cell survival.2

Since both folate and vitamin B12 deficiency can cause macrocytic anemia, appropriate treatment depends on the differential diagnosis of the deficiency. A serum folate concentration <3 ng/mL is considered to represent clinical deficiency by the World Health Organization and numerous subsequent clinical studies.6,7 Serum folate measurement provides an early index of folate status3; however, folate is much more concentrated in red blood cells than in serum so the red blood cell folate measurement more closely reflects tissue stores.5,8 Erythrocytes incorporate folate as they are formed, and levels remain constant throughout the life span of the cell. RBC folate levels are less sensitive to short-term dietary effects than are serum folate levels. Red blood cell folate concentration is considered the most reliable indicator of folate status.3

Low serum folate during pregnancy has been associated with neural tube defects in the fetus.9,10

In the 1990s mandatory increased fortification of enriched cereal-grain products along with the requirement of folate-related health and nutrient content claims on food and dietary supplement products significantly increased the folic acid content of the US food supply.11-13 Several reports have shown that serum folate concentrations have increased in the general US population since these measures were implemented.11-13

Specimen Requirements

Specimen

Serum

Volume

0.8 mL

Minimum Volume

0.3 mL (Note: This volume does not allow for repeat testing.)

Container

Red-top tube or gel-barrier tube

Collection

If a red-top tube is used, transfer separated serum immediately to a plastic transport tube. Avoid hemolysis.

Storage Instructions

Refrigerate

Stability Requirements

Temperature

Period

Room temperature

1 day

Refrigerated

7 days

Frozen

7 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Plasma specimen; hemolysis; improper labeling

Clinical Information

Special Instructions

This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

Footnotes

1. Folate on Elecsys 1010/2010 and Modular Analytics E170, package insert 2007-02, V 1, Indianapolis, Ind: Roche Diagnostics; 2007.
2. Miale JB. Hematology. Laboratory Medicine. St Louis, Mo: CV Mosby;1982:416-440.
3. Brewster MA. Vitamins. In: Kaplan LA, Pesce AJ, eds.Clinical Chemistry: Theory, Analysis, and Correlation. St. Louis, Mo: CV Mosby; 1989: 543-568.
4. Fairbanks VF, Klee GG. Biochemical aspects of hematology. In: Burtis CA, Ashwood ER, eds.Tietz Textbook of Clinical Chemistry. WB Saunders Co;1999:1642-1710.
5. McNeely MD. Folic acid. In: Pesce AJ, Kaplan LA, eds.Methods in Clinical Chemistry. St Louis, Mo: CV Mosby;1987:539-542.
6. Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency: A guide for the primary care physician. Arch Intern Med. 1999 Jun 28; 159(12):1289-1298. 10386505
7. Shane B. Folate status assessment history: Implications for measurement of biomarkers In NHANES. Am J Clin Nutr. 2011 Jul; 94(1):337S-342S. 10386505
8. Nutritional anemias. Report of a WHO group of experts. World Health Organ Tech Rep Ser. 1972; 503:1-29. 4626525
9. Wolff T, Witkop CT, Miller T, Syed SB; U.S. Preventive Services Task Force. Folic acid supplementation for the prevention of neural tube defects: An update of the evidence for the US Preventive Services Task Force. Ann Interv Med. 2009 May 5:150(9):632-639. 19414843
10. McNulty H, Cuskelly GJ, Ward M. Response of red blood cell folate to intervention: implications for folate recommendations for the prevention of neural tube defects. Am J Clin Nutr. 2000 May; 71(5 Suppl);1308S-1311S. 10799407
11. Choumenkovitch SF, Selhub J, Wilson PW, Rader JI, Rosenberg IH, Jacques PF. Folic acid intake from fortification in United States exceeds predictions. J Nutr. 2002 Sep;132(9):2792-2798. 12221247
12. Ganji V, Kafai MR. Trends in serum folate, RBC folate, and circulating total homocysteine concentrations in the United States: Analysis of data from National Health and Nutrition Examination Surveys, 1988-1994, 1999-2000, and 2001-2002. J Nutr. 2006 Jan; 136(1):153-158. 16365075
13. Pfeiffer CM, Johnson CL, Jain RB, et al. Trends in blood folate and vitamin B-12 concentrations in the United States, 1988 2004. Am J Clin Nutr. 2007 Sep; 86(3)718-727. 17823438

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
002014 Folate (Folic Acid), Serum 2284-8 002020 Folate (Folic Acid), Serum ng/mL 2284-8
Reflex Table for Folate (Folic Acid), Serum
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 002021 Note: 002021 Note: N/A

For Providers

Please login to order a test.

 

© 2017  Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.

CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2017, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf