Macrocytosis: pitfalls in testing and summary of guidance

doi:10.1136/bmj.39325.689641.471

BMJ 2007;335:884-886 (27 October), doi:10.1136/bmj.39325.689641.471

Practice

Cases in Primary Care Laboratory Medicine

Macrocytosis: pitfalls in testing and summary of guidance

Michael Galloway, consultant haematologist¹, Malcolm Hamilton, consultant haematologist and organiser of the UK NEQAS scheme for haematinic assays²

¹ City Hospitals Sunderland NHS Foundation Trust, Sunderland Royal Hospital, Sunderland SR4 7TP, ² Department of Haematology, Royal Devon and Exeter NHS Foundation Trust, Exeter EX2 5DW

Correspondence: M Galloway mike.galloway@nhs.net

Low vitamin B-12 levels can occur without deficiency being present,and normal levels don't always rule out vitamin B-12 deficiency.A clinical assessment, together with blood count and blood filmresults, can ensure a correct interpretation of vitamin B-12and folate levels

The first 150 words of the full text of this article appear below.

Introduction

Summary points

Macrocytosis is commonly associated with the use of severaldrugs and does not require further investigation unless thereare additional clinical features

Before testing, the probabilityof vitamin-B12 or folate deficiency should be undertaken byassessing relevant features in the history and examination

Myelodysplasticsyndromes often present as a macrocytic anaemia with normalvitamin-B12 and folate concentrations

When full blood countis normal, vitamin-B12 deficiency should be suspected in patientswith neurological signs and severe oropharyngeal ulceration

Deficiency of vitamin B-12 and folate classically causes a macrocyticanaemia, but macrocytosis may be due to causes other than deficiencyof vitamin B-12 and folate. Neurological changes due to vitaminB-12 deficiency may develop in the absence of changes in theblood count. Incorrect interpretation of vitamin B-12 levelsin particular can lead to a wrong diagnosis, inappropriate referralto hospital, and inappropriate investigation. We have publishedguidance on the indications for . . . [Full text of this article]

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