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Test Code IFBA Intrinsic Factor Blocking Antibody, Serum

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.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.


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

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

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.

Clinical Reference

1. Toh BH, Van Driel IR, Gleeson PA: Pernicious anemia. N Engl J Med. 1997;337:1441-1448. doi: 10.1056/NEJM199711133372007

2. Klee GG: Cobalamin and folate evaluation: measurement of methylmalonic acid and homocysteine vs vitamin B12 and folate. Clin Chem. 2000;46:1277-1283

3. Ward PC: Modern approaches to the investigation of vitamin B12 deficiency. Clin Lab Med. 2002:22;435-445. doi: 10.1016/s0272-2712(01)00003-8

4. Stabler SP, Allen RH: Vitamin B12 deficiency as a worldwide problem. Ann Rev Nutr. 2004;24:299-326. doi: 10.1146/annurev.nutr.24.012003.132440

5. Roberts NB, Taylor A, Sodi R: Vitamins and trace elements. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:639-718

6. Bizzaro N, Antico A: Diagnosis and classification of pernicious anemia. Autoimmun Rev. 2014;13(4-5):565-568. doi: 10.1016/j.autrev.2014.01.042

Report Available

1 day to 3 days

Method Name

Immunoenzymatic Assay