Overview

The Haematinics section of the Haematology laboratory at Cheltenham General Hospital processes Serum Vitamin B12, Folate, Ferritin and Intrinsic Factor antibody assays with the aid of two Beckman-Coulter Access2 Immunoassay analyers.

Please note:

  • B12 and Folate are no longer performed on elderly patients in the acute setting unless there is a specific indication, eg. macrocytosis +/- anaemia; (pan)cytopenia; blood film report comment.
  • Ferritins are no longer performed on elderly patients in the acute setting unless there is a specific indication.
  • B12, Folate and Ferritin assays will not be repeated if the assays have been performed within the last three months (with the exception of Ferritin assays on Haemochromatosis patients).

Serum Folate Assay

Serum folate falls rapidly with an inadequate diet despite sufficient body stores . It is however more reliably analysed than Red Cell folate and is therefore used to screen for folate deficiency.

The common causes of deficiency are inadequate diet, malabsorption, anti-folate drugs (especially anticonvulsants) and occasionally in association with any disease that causes increase cell turnover, e.g. exfoliation.

Serum Vitamin B12 Assay

Interpretation is difficult. The following observations are offered.

  • In clear cut deficiency, levels of B12 are nearly always <150 ng/l and usually <100 ng/l.
  • Pernicious anaemia is the cause of the majority of severe deficiencies in adults. 50% of patients with pernicious anaemia have intrinsic factor antibodies, while this antibody is rarely seen in normal controls. Parietal cell antibodies are present in 90% of patients but are also seen in 1 - 2% of normal controls.
  • Patients with B12 in the borderline range (150 - 180 ng/l) may have either early B12 deficiency, or be healthy "low normal".
  • Neurological disease or glossitis may occur without anaemia or macrocytosis and may be irreversible.
  • Interpretation of early megaloblastic change in the marrow is difficult and cannot be reliably distinguished from myelodysplasia.

The following is advised:

Testing should be restricted to those with a suspected vitamin B12 deficiency (macrocytosis, anaemia, neurological deficit, glossitis or clinical condition known to cause B12 deficiency) and should not be used as a screening test.

When the B12 level is less than 150 ng/l a presumptive diagnosis of B12 deficiency is made. Where the cause is not known, the laboratory will automatically check for intrinsic factor antibodies. If these are negative, a clinical decision has to be made as to whether further investigation is necessary for patient management. If the B12 is between 150 and 180 ng/l, a therapeutic trial should be given. If there is a clinical response then a diagnosis of B12 deficiency is made and the appropriateness of further investigation as to cause should be determined.

If there is no response, it is likely that the patient is not B12 deficient and other causes of the clinical problem must be sought.

If further investigation is required, please contact a Consultant Haematologist.

B12 Investigation and Treatment Algorithm

B12 Maintenance

Intrinsic Factor Antibody Assay

Notes:

  • An intrinsic factor antibody assay will not be repeated if the assay has been performed in the previous 12 months.
  • A negative result with this test does not rule out a diagnosis of pernicious anaemia.
  • It is not possible to test for intrinsic factor antibodies in patients with a high B12 level.
  • If the B12 result is normal, an intrinsic factor antibody assay will not be performed. Please discuss directly with the Haematology laboratory if Intrinsic Factor testing is required (high clinical suspicial of autoimmune B12 deficiency) as, rarely, a normal B12 result may be generated in the presence of high titre intrinsic factor antibodies.

Serum / Plasma Ferritin Assay

Please note: Ferritin is an acute phase protein and may give an unreliable estimate of iron status in patients with co-existent inflammatory disease.

If a Ferritin assay is being requested on a patient with Haemachromatosis, please state this clearly on the request form.

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