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Q Should I treat a well, non-anaemic woman in her mid-20s who has a low vitamin B12 and folate but negative intrinsic factor (IF) and coeliac autoantibodies and a balanced diet?

A This depends on how low the levels are. Significantly low results of either haematinic certainly warrant treatment and further investigation to rule out malabsorption of either or both vitamins. Borderline results may be monitored only at this stage but possible causes need consideration.

Red cell folate (RCF) levels without significant clinical deficiency are often low with vitamin B12 deficiency and the converse is also true. Thus the patient may not truly have combined deficiency.

The dietary history is important. Although she is not vegan/vegetarian, many patients have diets lacking in both haem iron (animal derived) and non-haem iron. A drug history may also help: oral contraceptive use is associated with low B12 levels while alcohol may cause both low folate and B12 levels.

A low B12 level, in the absence of any significant history, may suggest early pernicious anaemia (PA). Negative IF antibodies do not exclude PA as they are only positive in 50-60 per cent of cases. Gastric parietal cell antibodies are seen in 95 per cent of cases and, although there is an overlap with other autoimmune diseases and with normal individuals, a negative result makes PA unlikely.

If B12 levels are particularly low, i.m. B12 should be given and a haematology referral made. In borderline cases, a response to oral B12 may be diagnostic and therapy should be discussed with the local haematology department.

If RCF levels are particularly low and dietary deficiency unlikely, refer to exclude malabsorption or chronic inflammatory states. With borderline levels a response to physiological doses of folic acid may be diagnostic of dietary deficiency. B12 deficiency must be excluded or concurrently treated as folic acid alone may mask neurological symptoms.

Dr Kate Ryan,

consultant haematologist, Manchester Royal Infirmary

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