Haematinic Testing

Page created by Mark Crowther on 10th June 2019.  Due for Review 10th June 2020.

Introduction

1. Ferritin, B12 and Folate are important diagnostic tests, mainly but not exclusively for the investigation of anaemia.
2. Ferritin is tested by Biochemistry and B12/Folate by Haematology. They should all be sent to the lab in serum gel tubes
3. The appropriate indications for testing are given below.

Ferritin

1. Microcytic anaemia or microcytosis
2. Unexplained normocytic/normochromic anaemia
3. Malabsorption/poor diet/gastrointestinal disease
4. Anaemia in pregnancy
5. Anaemia in Chronic Kidney Disease (also request iron studies)
6. Iron overload (also check fasting iron studies)

Cautions for Serum Ferritin Testing

1. Normal levels are 30-400ng/ml in men and 13-300ng/ml in women.
2. Ferritin and CRP are both acute phase reactants. It makes sense therefore to check CRP when requesting ferritin as interpretation of ferritin may be tricky if CRP raised.
3. A microcytic hypochromic anaemia with a haemoglobin <80g/L is unlikely to be due to infection/inflammation and more likely to be due to iron deficiency
4. A patient with anaemia and ferritin >100 is unlikely to have significant iron deficiency, even if the CRP is raised
5. A patient with anaemia and ferritin in the normal range but <100, whose CRP is raised, may have iron deficiency. Consider a trial of iron replacement.

B12/Folate

1. Macrocytosis
2. Malabsorption/poor diet/gastrointestinal disease
3. Pancytopenia
4. Pre-dialysis
5. Effectiveness of oral replacement therapy
6. Unexplained neurological / neuropsychiatric symptoms eg. peripheral neuropathy/ sensory ataxia/ ambylopia/parasthesia; (newly diagnosed) dementia; visual loss.
7. Oral ulceration/ glossitis/ beefy tongue/ angular stomatitis.
8. On metformin for >10 years needs annual testing

Cautions for Serum Folate Testing

1. Normal levels are 3.9-20.0ng/ml.
2. Tiredness is NOT an indication for testing; testing may be declined without further clinical information. Please check FBC first.
3. Low Serum Folate levels may represent true deficiency or may be secondary to acute illness. Consider full clinical context, other haematological parameters (haemolysis, unexplained anaemia, raised MCV) and evidence of any underlying causes.
4. Falsely-reduced serum folate levels can occur in patients with anorexia, acute alcohol consumption, normal pregnancy and during anti-convulsant therapy.
5. Results should be considered within the full clinical context, and in conjunction with any concurrent B12 deficiency results.
6. Lower Folate levels are seen in patients taking the combined oral contraceptive pill/ HRT. These levels are generally not clinically significant. Testing should NOT be undertaken in these situations unless one of the indications above is also present.

Cautions for Vitamin B12 Testing

1. Normal levels are 110-569pmol/l
2. Tiredness is NOT an indication for testing; testing may be declined without further clinical information. Please check FBC first.
3. Lower B12 levels are seen in patients taking the combined oral contraceptive pill/ HRT. These levels are generally not clinically significant. Testing should NOT be undertaken in these situations unless one of the indications above is also present.
4. Low B12 levels, mild macrocytosis and mild thrombocytopenia (platelets 100-149,000) are not uncommon in pregnancy and can be due to normal physiological changes. B12 replacement may be considered if platelets <100 or unexplained macrocytic anaemia is present.
5. If patient is on IM B12 replacement, repeat B12 testing is not indicated but FBC and reticulocyte response should be monitored.

Content by Dr Mark Crowther