Normal: 243-894 pg/mL Indeterminant: 175-242 pg/mL Deficient: < 174 pg/mL

If plasma is sent and Intrinsic Factor Blocking Antiboies (IFBA) is reflexively ordered, the laboratory will call for an additional r ed top tube if IFBA is required. Intrinsic factor antibody automatically analyzed if B12 result is <243 pg/ml. Patient is charged for IFBA result. New analytical immunoassay with different reference ranges instituted 4/24/00 at 10:00.

The assay is unaffected by icterus (bilirubin is less than 65 mg/dL), hemolysis (Hb is less than 1.0 g/dL), lipemia (triglycerides is less than 1500 mg/dL) and biotin is less than 50 ng/mL. (criterion: recovery within plus or minus 10% of initial value). 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 1500 U/mL. In vitro tests were performed on 54 commonly used pharmaceuticals. No interference with the assay was found. In rare cases interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur. For diagnostic purposes, the vitamin B12 findings should always be assessed in conjunction with the patient's medical history, clinical examination and other findings.