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Folate status as measured by red blood cell folate
This indicator describes the use of red blood cell folate as a biological indicator of folate stores.
Individuals who consume folate-containing foods or foods that are fortified with folic acid may improve their folate status as noted by red blood cell folate (1), helping them avoid the negative consequences of folate deficiency or insufficiency. Adequate folate status in women of childbearing age protects against neural tube defects in early pregnancy and other negative reproductive health outcomes (2). Red blood cell folate reflects long-term status over the last 3–4 months (2) and is not affected by recent dietary intake (3).
The folate status of the target population, as measured by red blood cell folate concentration
Red blood cell folate concentrations can be presented as the average concentration in the population or by using a cut-off value to determine the percentage of the population with deficiency, as well as insufficiency.
Average red blood cell folate concentration
Numerator: the sum of red blood cell folate concentrations for each individual assessed
Denominator: the number of persons assessed
• Divide the numerator by the denominator to obtain the average.
Percentage of the population with folate deficiency, lower than 151 ng/mL (340 nmol/L) (2, 4)
Numerator: the number of individuals classified as having a folate deficiency
Denominator: the number of persons assessed
• Divide the numerator by the denominator. Multiply the result by 100 to convert the number into a percentage.
Percentage of the population of women of reproductive age with folate insufficiency, 400 ng/mL (906 nmol/L) or lower (2, 5)
Numerator: the number of women of reproductive age classified as below the cut-off value
Denominator: the number of women of reproductive age assessed
• Divide the numerator by the denominator. Multiply the result by 100 to convert the number into a percentage.
Considerations for the calculations:
• There are several cut-off values to consider. Using homocysteine concentrations as a metabolic indicator, the cut-off value for determining folate deficiency in all age groups is defined as red blood cell folate lower than 151 ng/mL (340 nmol/L) (2, 4).
• Using macrocytic anaemia as a haematological indicator, deficiency is defined as red blood cell folate lower than 100 ng/mL (226.5 nmol/L) in all age groups (2).
• At the population level, red blood cell folate concentrations should be 400 ng/mL (906 nmol/L) or higher in adult women of reproductive age, to achieve the greatest reduction of neural tube defects. Values below this level indicate folate insufficiency (2, 5).
assessment, folate deficiency, folate insufficiency, folate status, folic acid, micronutrient status, nutritional status, red blood cell
All
Outcome
Improved nutritional status
School age children, 12-23 months, 24-35 months, 36-47 months, 48-59 months, 6-11 months, Adolescents, Men, Other (not any of the above, post-menopausal women, elderly), Women of reproductive age
None,
Folate
Community, Health systems, Market-based
The collection of biological markers of status, such as red blood cell folate, requires laboratory expertise.
Microbiological assay is recommended as the most reliable method to obtain comparable results for red blood cell folate across countries (2, 5).
Measurement of red blood cell folate is useful to understand long-term folate stores in the population.
Red blood cell folate may be expensive to analyse, depending on the method used, which might limit the ability to use this indicator. The collection and analysis of biological indicators of micronutrient status requires laboratory expertise to collect, process, store and analyse, which might be a limitation for the use of these indicators in some contexts.
Eighty non-pregnant and non-lactating women of reproductive age were randomly selected to participate in a cross-sectional survey where red blood cell folate status was measured. One woman had a red blood cell folate value less than 151 ng/mL and 25 women had red blood cell folate values below 400 ng/mL
Folate deficiency
Numerator (red blood cell folate level lower than 151 ng/mL ): 1
Denominator: 80
Calculation: 1/80 * 100 = 1.3% of women sampled had red blood cell folate deficiency.
Insufficiency
Numerator (red blood cell folate level lower than 400 ng/mL): 25
Denominator: 80
Calculation: 25/80 * 100 = 31.3% of women sampled had red blood cell folate insufficiency.
1. Pfeiffer CM, Hughes JP, Lacher DA, Bailey RL, Berry RJ, Zhang M et al.
Estimation of trends in serum and RBC folate in the US population from pre- to postfortification using assay-adjusted data from the NHANES 1988–2010. J Nutr. 2012;142:886–93. doi:10.3945/jn.111.156919.
2. Serum and red blood cell folate concentrations for assessing folate status in populations. Vitamin and Mineral Nutrition Information System. Updated 2015. Geneva: World Health Organization; 2015 (WHO/NMH/NHD/EPG/15.01; http://apps.who.int/iris/bitstream/10665/162114/1/WHO_NMH_NHD_EPG_15.01.pdf, accessed 6 October 2015).
3. Green R. Indicators for assessing folate and vitamin B12 status and for monitoring the efficacy of intervention strategies. Am J Clin Nutr. 2011;94:666S–72S. doi:10.3945/ajcn.110.009613.
4. Conclusions of a WHO Technical Consultation on folate and vitamin B12 deficiencies. Food Nutr Bull. 2008;29:S238–44.
5. Guideline: Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects. Geneva: World Health Organization; 2015 (http://apps.who.int/iris/bitstream/10665/161988/1/9789241549042_eng.pdf?ua=1, accessed 6 October 2015).