Folate, Hemolysate

This is an intermediary biomarker that is used to calculate Folate, RBC. There is no reference range provided by the laboratory, hence please refer to the actual "Folate, RBC" marker instead. 

A hemolysate is a product resulting from hemolysis which is defined as the liberation or separation of the hemoglobin from the red blood corpuscles and its appearance in the fluid in which the corpuscles are suspended. Hemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs.

The Folate RBC result is obtained using a hemolysate prepared from whole blood. The Folate RBC result includes folate present in the RBCs and in the plasma. In order to obtain the folate concentration only in the RBCs, both specimens are required and a calculation is performed using results from both assays to obtain a corrected RBC Folate result.

Hemolysate is prepared first which is then treated with freshly prepared ascorbate solution. The resulting hemolysate is assayed and the result is calculated using the given formula:

RBC Folate = Hemolysate folate X 2100/hematocrit (%) 

What is folate?

Folate is a water-soluble vitamin essential for cell growth and division.

What is RBC folate?

- RBC folate provides information about folate status over the lifetime of RBCs, similar to hemoglobin A1C as used in blood glucose monitoring. Approximately 5% of people with normal serum folate levels may have evidence of folate deficiency if analyzed using RBC folate testing.

- RBC folate determination is obtained by measuring the folate concentration in a whole blood (WB) hemolysate solution and dividing it by the patient’s hematocrit (hematocrit = the ratio of the volume of red blood cells to the total volume of blood).

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The measurement of folate in red blood cells (RBCs) is preferred since it reflects long-term folate status in the body compared to plasma/serum folate which may be influenced by recent dietary intake. The commonly accepted technique for RBC folate analysis involves preparation of a hemolysate using a fresh whole blood sample.

Hematocrit and plasma folate concentrations are needed to calculate RBC folate values.

Folate is essential for normal metabolism, DNA synthesis and red blood cell regeneration. Untreated deficiencies may lead to megaloblastic anemia. For diagnosis of folate deficiency, it is recommended to perform determinations not only in serum but also in erythrocytes. More than 95 % of folate occurs in the red blood cells. The folate concentration in erythrocytes more truly reflects the overall folate concentration in the tissue while the serum or plasma level reflects the preceding uptake of folates from the food and fluctuates significantly with the diet. Following dietary deprivation of folate, serum levels decline within 3 weeks, but RBC folate levels remain the same for 3–4 months. Therefore, the Folate RBC assay is used as an aid in the diagnosis of folate deficiency in erythrocytes.

References:

- https://academic.oup.com/ajcp/article/149/suppl_1/S187/4801705

- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1770141/