|Red top tube 5 mL (Clot Activator)
Call laboratory for additional acceptable specimen collection containers.
3 mL; red top or TWO Microtainer® devices.
Hemolyzed and plasma samples are NOT acceptable.
Deliver to laboratory immediately after collection.
Collect a fasting sample.
24 hrs/day, 7 days a week, including holidays.
1 hour (upon receipt in laboratory)
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
The assay is unaffected by icterus (bilirubin is less than 33
mg/dL), lipemia (triglycerides is less than 1500 mg/dL), hemolysis (Hb
less than 40 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
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.