Normal: > 4.1 ng/mL Indeterminate: 2.2 - 4.1 ng/mL Deficient: < 2.2 ng/mL All enriched grains have been fortified with folic acid in the U.S. since 1998 and therefore the prevalence of folate deficiency is low (1%). Testing for folate deficiency is strongly discouraged unless profound malnutrition is suspected and other causes of anemia have been excluded.

The assay is unaffected by icterus (bilirubin is less than 33 mg/dL), lipemia (triglycerides is less than 1500 mg/dL) and biotin is less than 40 ng/mL. (criterion: recovery within plus or minus 0.5 ng/mL (1.1 nmol/l) at folate levels is less than 5 ng/mL (11 nmol/l), or within plus or minus 10% at folate levels is greater than 5 ng/mL (11 nmol/l). In patients receiving therapy with high biotin doses (i.e. is greater than 5 mg/day) no sample should be taken until at least 8 hours after the last biotin administration. No interference was observed from rheumatoid factors up to a concentration of 400 U/mL. In vitro tests were performed on 56 commonly used pharmaceuticals. No interference with the assay was found. Folate assays of samples from patients receiving therapy with certain pharmaceuticals, e.g. methotrexate or leucovorin, are contraindicated because of the cross-reactivity of folate binding protein with these compounds. In rare cases interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur. For diagnostic purposes, the Folate findings should always be assessed in conjunction with the patient's medical history, clinical examination and other findings.