Folic acid or folate is a water-soluble vitamin from the B group and is involved in one-carbon metabolism. Folate deficiency or inadequate folate intake is associated with anaemia, neural tube defects and neuropsychiatric disorders. Furthermore, insufficient dietary intake of folate results in elevated plasma homocysteine, which is a risk factor for cardiovascular disease.

As with most other vitamins, the assessment of biological stores and intake is based on the concentration in body fluids. Studies of folate status have traditionally used serum/plasma or red blood cell folate. Both assays are widely available in laboratories. Red cell folate, favoured by many clinicians, is the more labour-intensive test and therefore more costly than serum …