Microcytosis, iron deficiency and thalassaemia in a multi-ethnic community: a pilot study

The high prevalence of microcytosis (defined here as mean cell haemoglobin<27 pg) with no other abnormality is a principal cause of confusion in screening for haemoglobin disorders. Here we report the results of a small pilot study aiming to resolve this confusion by routinely proceeding to plasma ferritin and HPLC assay, using the original sequestrene blood sample, when microcytosis is detected. Participants comprised a random sample of 1,302 people referred for a full blood count by their General Practitioner (GP) to the laboratory of a North London district general hospital serving a multi-ethnic inner-city population. Ethnicity was established by questionnaire. In North Europeans, microcytosis was present in 3% of males (half were iron-deficient) and 11% of females (most were iron-deficient). Among ethnic minorities, microcytosis was present in 35% of males (one tenth were iron-deficient), and 45% of females (less than half were iron-deficient): an exclusion diagnosis of "probable alpha thalassaemia" could be made in the remainder. We conclude that when microcytosis is present, routine further analysis of the original sequestrene sample by plasma ferritin assay and haemoglobinopathy screening could lead to a more efficient and cost-effective laboratory service for primary care and maternity services.