I found this IFAB test guideline. I found a few things pretty interesting. This particular lab which is the lab that did my IFAB test says that you should be fasting for 8 hours before you take this test and you should not have had any B12 injections within 2 weeks prior to the test. Another interesting thing I found was near the end under clinical information, where it says that an IFAB test could be positive for people with rheumatoid arthritis or other autoimmune diseases such as thyroid disease could cause a positive IFAB test without having pernicious anemia. But could lead to PA in the future. I found this interesting. Since Lyme disease and rheumatoid arthritis often get confused by each other, could Lyme disease also give you a positive IFAB test? ( sorry Lyme is not an autoimmune disease but can cause them. It is a virus caused by a tick bite. I said that wrong. Sorry.) thanks Jillymo
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Logan Health Medical Center Laboratory Test Catalog
Logan Health Medical Center Laboratory Test Catalog
powered by Mayo Clinic Laboratories
Test Code IFAB
Intrinsic Factor Blocking Antibody, Serum
Additional Codes
Mayo Test ID
IFBA
Reporting Name
Intrinsic Factor Blocking Ab, S
Useful For
Confirming the diagnosis of pernicious Anemia
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum
Ordering Guidance
For a comprehensive workup of patients with suspected pernicious anemia, order ACASM / Pernicious Anemia Cascade, Serum, which initiates testing with measurement of vitamin B12. Depending of the vitamin B12 concentration, testing for intrinsic factor blocking antibody, gastrin, and methylmalonic acid may be added.
Specimen Required
Patient Preparation:
1. Patient should be fasting for 8 hours.
2. This test should not be performed on patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks.
Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 1 mL
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 14 days
Frozen 14 days
Special Instructions
Vitamin B12 Deficiency Evaluation
Reference Values
Negative
Day(s) Performed
Monday through Friday
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
CPT Code Information
86340
LOINC Code Information
Test ID Test Order Name Order LOINC Value
IFBA Intrinsic Factor Blocking Ab, S 31444-3
Result ID Test Result Name Result LOINC Value
IFBLA Intrinsic Factor Blocking Ab, S 31444-3
CMT31 Comment 48767-8
Clinical Information
The cobalamins, also referred to as vitamin B12, are a group of closely related enzymatic cofactors involved in the conversion of methylmalonyl-coenzyme A to succinyl-coenzyme A and in the synthesis of methionine from homocysteine. Vitamin B12 deficiency can lead to megaloblastic anemia and neurological deficits. The latter may exist without, or precede, anemia. Adequate replacement therapy will generally improve or cure cobalamin deficiency. Unfortunately, many other conditions, which require different interventions, can mimic the symptoms and signs of vitamin B12 deficiency. Moreover, even when cobalamin deficiency has been established, clinical improvement may require different dosages or routes of vitamin B12 replacement, depending on the underlying cause. In particular, patients with pernicious anemia (PA), possibly the most common type of cobalamin deficiency in developed countries, require either massive doses of oral vitamin B12 or parenteral replacement therapy. This is due to patients with PA having gastric mucosal atrophy, most likely caused by a destructive autoimmune process. This results in diminished or absent gastric acid, pepsin, and intrinsic factor (IF) production. Gastric acid and pepsin are required for liberation of cobalamin from binding proteins, while IF binds the free vitamin B12, carries it to receptors on the ileal mucosa, and facilitates its absorption. Most PA patients have autoantibodies against gastric parietal cells or IF, with the latter being very specific but only present in approximately 50% of cases. By contrast, parietal cell antibodies are found in approximately 90% of PA patients, but are also found in a significant proportion of patients with other autoimmune diseases and in approximately 2.5% (4th decade of life) to approximately 10% (8th decade of life) of healthy individuals.
Interpretation
The aim of the work-up of patients with suspected vitamin B12 deficiency is to first confirm the presence of deficiency and then to establish its most likely etiology.
Measurement of serum vitamin B12, either preceded or followed by serum methylmalonic acid measurement, is the first step in diagnosing pernicious anemia (PA). If these tests support deficiency, then intrinsic factor blocking antibody (IFBA) testing is indicated to confirm PA as the etiology. A positive IFBA test very strongly supports a diagnosis of PA. Since the diagnostic sensitivity of IFBA testing for PA is only around 50%, an indeterminate or negative IFBA test does not exclude the diagnosis of PA. In these patients, either PA or another etiology, such as malnutrition, may be present. Measurement of serum gastrin levels will help in these cases. In patients with PA, fasting serum gastrin is elevated to more than 200 pg/mL in an attempted compensatory response to the achlorhydria seen in this condition.
For a detailed overview of the optimal testing strategies in PA diagnosis, see ACASM / Pernicious Anemia Cascade, Serum and associated Vitamin B12 Deficiency Evaluation.
Cautions
Patients who have received a vitamin B12 injection or radiolabeled vitamin B12 injection within the previous 2 weeks may have high serum vitamin B12 levels, which can interfere with this assay leading to falsely elevated results.
Some patients with other autoimmune diseases may have positive intrinsic factor blocking antibody (IFBA) assays without suffering from pernicious anemia (PA). This is reported particularly in patients with autoimmune thyroid disease or type I diabetes mellitus. In the validation of this assay, 24 individuals with these autoimmune endocrine diseases were tested and all were IFBA negative. However, 5 of 15 of patients with rheumatoid arthritis were IFBA positive during the validation of this assay. The literature suggests such individuals may, in fact, be at risk of later development of PA.
Since this is a competitive binding assay, the risk of heterophile antibody interference is low. During validation, 24 human antimouse antibody positive specimens and 25 specimens with other heterophile antibodies were tested and all were IFBA negative. However, if the clinical picture does not agree with the IFBA test result, the laboratory should be consulted for advice.
Report Available
1 day to 3 days
Reject Due To
Gross hemolysis Reject
Gross lipemia OK
Method Name
Immunoenzymatic Assay
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A clinical picture of a B12 deficiency and PA explained.........
Various B12D/PA resources 
Intrinsic Factor at top of range
Gut Instinct
Post-treatment lab results -- interpretation help appreciated!
