RBC Folate Vs Serum Folate Testing: Know The Difference

Comparison Folate testing is important to find out what's wrong with your health and monitor conditions like anemia and red blood cell health. Folate testing can help detect nutritional deficiencies and potential health risks early on. But it is important to understand the difference between red blood cell (RBC) folate and serum folate to ensure the testing is accurate.

What is RBC Folate?

RBC folate, or red blood cell folate, measures the B9 vitamin in an individual's red blood cells. B9, also known as folic acid or folate, plays an important role in cell and tissue growth, as well as in DNA production and repair. Thus, an RBC folate test looks at the level of folic acid in an individual's red blood cells.

RBC Folate:

- Reveals the body's long-term circulating folate levels 

- Red Blood Cell (RBC) test measures the amount of folate stored in the body, indicating a more accurate indication of overall folate status

- Measure in terms of picomoles of folate per liter (pmol/L) 

- Sample collection requires only a finger-prick test 

- Ability to assess folate deficiency or sufficiency 

What is Serum Folate?

Serum folate, on the other hand, is a measure of the folic acid circulating in the blood. It shows how much folate gets into the blood after being eaten or taken as a supplement.

Serum Folate: 

- Measures folate levels in serum or plasma 

- Test measures levels of circulating folate in the blood at the time of collection 

- Measure in terms of nanomoles per each liter of blood sample (nmol/L) 

- Sample collection requires a larger sample than the RBC folate test 

- Used to help detect more serious folate deficiencies 

RBC Folate vs Serum Folate – The Difference

The primary difference between red blood cell folate and serum folate is in their sources. RBC folate is derived from red blood cells. It shows how much folate a person has taken in over the past few weeks, while serum folate shows how much folate has been circulating in the blood over the past few hours.

The following table presents a comparison between RBC folate and Serum folate:

Indications for Folate Testing

• A patient may undergo a folic acid test to detect megaloblastic anaemia and hypersegmented neutrophils.
• One way to look for folate deficiency is to check the level of folic acid in the blood or serum. Fasting readings are more accurate since serum levels are more susceptible to misleading increases following a meal.
• When serum RBC levels are low or low-normal, they should not be used as a screening test. Instead, they should be used as diagnostic tests. 
• However, the RBC folate test is more accurate, but it is more expensive and less common. 
• If the homocysteine level in the blood is high, but the MMA level is normal, this is also a sign of folate deficiency.

Normal Range

Folate levels can be used to determine if someone has megaloblastic anemia and treat it. Depending on how old you are, a different range of values for your plasma folate concentration should be considered normal.

• Adults - 2ng/mL to 20 ng/mL, 2μg/L to 20 μg/L, or 4.5nmol/L to 45.3 nmol/L
• Children - 5ng/mL to 21 ng/mL, 5μg/L to 21 μg/L, or 11.3nmol/L to 47.6 nmol/L
• Infants - 14ng/mLto -51 ng/mL, 14μg/L to 51 μg/L, or 31.7nmol/L to 115.5 nmol/L

The reference range for the level of folate in red blood cells (RBC) also changes with age, as shown below:

• Adults: 140ng/mL to 628 ng/mL or 317nmol/L to1422 nmol/L
• Children: Over 160 ng/mL or over 362 nmol/L

Interpretation

• The amount of folate in your blood is strongly affected by what you've eaten recently, and it's not a good way to measure how much is in your tissues. 
• With one meal full of folate, the folate level in the blood can be returned to normal. 
• Folate is mostly found in the liver, spinach, beans, and orange juice. However, cereal is often the main source of folate in countries that add folic acid to cereal.
• RBC folate gives information about folate levels over the life of RBCs, similar to how hemoglobin A1C is used to check blood sugar levels. 
• RBC folate testing can show that about 5% of people with normal serum folate levels have signs of folate deficiency.

When is RBC Folate Used?

Folate testing of the red blood cells (RBC) is a common way to determine if a person doesn't get enough folic acid. If your red blood cell folate levels are low, it may indicate that you aren't getting enough folic acid, that you don't absorb it very well, or that you need more. 

RBC folate testing may also be helpful for individuals with a liver illness or who use drugs that make it difficult to absorb folate since these situations are the same as those with liver disease.

When is Serum Folate Used?

Folate levels in the blood are often checked in pregnant women and other people who are more likely to have health problems if they don't get enough folate. In addition, it is often used to determine whether or not individuals take their folic acid or folate pills as directed. Inadequate vitamin B12 may also be identified with this test, as can megaloblastic anaemia.

Conclusion

To detect and monitor anaemia and other conditions linked to the health of red blood cells, it is necessary to do both a complete blood count and a serum folate test.

Folic acid status can be checked by measuring the amount of folate in red blood cells and serum. You must get the proper test for the most up-to-date and precise reading on your folate levels. If you know where you are in terms of your folate levels, you may take steps to ensure they remain optimal.

You and your doctor may be able to figure out what's wrong with you and how to treat it best if you and your doctor can tell the difference between these two tests and know when to order each one. Seek advice from your physician or other healthcare providers if you're unsure which test is right for you.

At Metropolis Healthcare, our diagnosticians have a lot of experience with accurate and reliable folate testing. Get in touch with us right away so that we can make sure your healthcare requirements are met most appropriately.