Specimen

Serum

Collection Medium:

Alternate
Collection Media:

Call laboratory for additional acceptable specimen collection 
containers.

Minimum:

2 mL; red top (sufficient for both B12 and serum folate)
or THREE 0.4 mL red top microtubes from a fasting patient.

Rejection Criteria:

Hemolyzed and plasma samples are NOT acceptable.

Delivery Instructions:

Deliver to laboratory immediately after collection.

Specimen
Instructions:

Collect a fasting sample.

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Analytic Time:

2 hours (upon receipt in laboratory)

Reference Range:

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.

Comments:

New analytical immunoassay with different reference ranges instituted 
4/24/00.

Test
Limitations:

The assay is unaffected by icterus (bilirubin is less than 40 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.

Methodology:

Electrochemiluminescence Immunoassay

CPT Code:

82746

See also:
Folate (RBC), Whole Blood

See Additional Information:
Fasting Specimen Requirements
Specimens Requiring Immediate Delivery