Intrinsic Factor Blocking Antibody, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Confirming the diagnosis of pernicious anemia
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
See Pernicious Anemia Testing Cascade in Special Instructions.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Intrinsic Factor Blocking Ab, S
Anti Intrinsic Factor
Type 1 Intrinsic Factor Antibody
Intrinsic Factor Blocking Antibody
Type 1 Intrinsic Factor Antibody
Intrinsic Factor Blocking Antibody
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 1 mL
Additional Information: This test should not be ordered on patients who have received vitamin B12 injection within the last 2 weeks.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross OK
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum||Refrigerated (preferred)||14 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 anemia, or precede it. 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 commonest type of cobalamin deficiency in developed countries, require either massive doses of oral vitamin B12 or parenteral replacement therapy. The reason is that in PA patients suffer from 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 intrinsic factor, 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.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
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 supports very strongly 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 >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/83632 Pernicious Anemia Cascade, Serum, and associated Pernicious Anemia Testing Cascade in Special Instructions.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Do not order intrinsic factor blocking antibody (IFBA) testing in patients who have received a vitamin B12 injection within the last 2 weeks. High free serum vitamin B12 levels, as may be seen within the first 2 weeks after a vitamin B12 injection, can interfere in the IFBA assay, leading to false-positive results. We reflex all positive IFBA tests that have not been ordered through the Pernicious Anemia Cascade to vitamin B12 measurement. If this yields a level >800 ng/L, we append a comment to the report indicating a possible false-positive result.
Some patients with other autoimmune diseases may have positive IFBA assays without suffering from pernicious anemia (PA). This is reported inparticular 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 assay, the risk of heterophile antibody interference is low. During validation, 24 human anti-mouse 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.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Toh BH, Van Driel IR, Gleeson PA: Pernicious anemia. N Engl J Med 1997;337:1441-1448
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
4. Stabler SP, Allen RH: Vitamin B12 deficiency as a worldwide problem. Ann Rev Nutr 2004;24:299-326
Method Description Describes how the test is performed and provides a method-specific reference
The instrument used is a Beckman Coulter Unicel DXI 800. The Access Intrinsic Factor Antibody assay is a competitive binding immunoenzymatic assay. A sample is added to a reaction vessel along with intrinsic factor alkaline phosphatase conjugate and a protein blocking solution. Intrinsic factor antibody in the sample binds to the intrinsic factor conjugate. After incubation in a reaction vessel, paramagnetic particles coated with a mouse monoclonal, specific for the vitamin B12 binding site on intrinsic factor, is added to the reaction. Intrinsic factor conjugate that has not been blocked by sample anti-intrinsic factor binds to the monoclonal antibody on the solid phase. After an additional incubation in the reaction vessel, 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 intrinsic factor antibody in the sample expressed in AU/mL (Antibody Units/mL). The amount of analyte in the sample is determined from a stored calibration. (Beckman Coulter Assay Manual 2009, Beckman Coulter Inc., Fullerton, CA)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 5 a.m.-12 p.m., Saturday; 6 a.m.-6 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. 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 Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|IFBLA||Intrinsic Factor Blocking Ab, S||31444-3|