Macrocytosis (Guidelines)

Audience

• Highland HSCP 

The normal MCV depends on age but is generally 83 to 101 fL. This can be present with or without anaemia.

Causes

• Artifact e.g. delay to analysis
• Alcohol and liver disease
• Medications especially hydroxycarbamide, methoxtrexate, chemotherapy and other immunomodulatory drugs
• Thyroid dysfunction
• Vitamin B12 or folate deficiency
• Haemolysis (due to reticulocytosis)
• Paraprotein
• Pregnancy
• Myelodysplasia and aplastic anaemia – often associated with neutropenia and/or thrombocytopenia

History and examination

Suggest looking at the above causes and look for signs of liver disease. Review older blood test results. Ask about diet and malabsorption.

Suggested investigations

• Liver function tests
• Vitamin B12 and folate
• Blood film
• Haemolysis screen (reticulocytes, blood film, DAT, LDH, haptoglobin)
• Pregnancy test
• Immunoglobulins and serum protein electrophoresis
• TSH

Management 

• Correct any secondary cause and consider repeating test in first instance
• If haemolysis is suspected then please discuss or refer
• If myelodysplasia is suspected (other cytopenias or blood film abnormalities) then please discuss or refer
•  Please consider referral for macrocytic anaemia when the haemoglobin is persistently less than 110 g/L in men or less than 100g/L in women and there are no secondary causes. For cases when the haemoglobin is still greater than 100g/L a discussion via Clinical Dialogue may appropriate especially if the patient is asymptomatic.
• If the MCV is high with no anaemia or other cytopenia and no cause is identified then these patients can be monitored in primary care every six to 12 months
• If patient has liver disease please discuss with the G.I./ hepatology tea
•  If a paraprotein is detected then please see separate guideline on this finding