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HelpTest Code LAB857 Intrinsic Factor Blocking Antibody, Serum
Additional Codes
IFBA
Useful For
Confirming the diagnosis of pernicious anemia
Testing Algorithm
For more information, see Vitamin B12 Deficiency Evaluation.
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumOrdering 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 |
On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318
Send in plastic vial, Refrigerated
Off-campus collections:
Centrifuge and aliquot within 2 hours.
Specimen to be stored/transported at Refrigerated temp.
Special Instructions
Reference Values
Negative
Day(s) Performed
Monday through Friday
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.
Method Description
The Access Intrinsic Factor (IF) Antibody assay is a competitive binding immunoenzymatic assay. The sample is added to a reaction vessel along with IF alkaline phosphatase conjugate and a protein blocking solution. IF antibody in the sample binds to the IF conjugate. After incubation in a reaction vessel, paramagnetic particles coated with a mouse monoclonal antibody, specific for the vitamin B12 binding site on IF, is added to the reaction. IF conjugate that has not been blocked by sample anti-IF binds to the monoclonal antibody on the solid phase. After an additional incubation, materials bound to the solid phase are held in a magnetic field, while unbound materials are washed away. Chemiluminescent substrate is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is inversely proportional to the concentration of IF antibody in the sample expressed in AU/mL (antibody units/mL). The amount of analyte in the sample is determined from a stored calibration.(Package insert: Access Intrinsic Factor Ab. Beckman Coulter, Inc; 06/2020)
Report Available
1 day to 3 daysSpecimen Retention Time
2 weeksReject Due To
| Gross hemolysis | Reject |
| Gross lipemia | OK |
Method Name
Immunoenzymatic Assay