It is now 30 years since the first ICSH recommendations were published (International Committee for Standardization in Haematology, 1979) concerning the quantification of Haemoglobin F (Hb F); and during this time, there have been several new analytical developments in the field, and therefore the ICSH Board consider that the original recommendations should be revised.

 

Hb F is a haemoglobin tetramer composed of two α and two γ globin chains (α2γ2). It is a normal haemoglobin and is the major haemoglobin present in the fetus but is gradually replaced after birth by Hb A (α2β2) as the γ chains are replaced by β chains.

 

The measurement of Hb F in red cells is clinically useful in the diagnosis of δβ thalassaemia because the amount of Hb F is raised in this condition. Hb F is also slightly raised (1–5%) in pregnancy (Pembrey, Weatherall & Clegg, 1973), in hereditary persistence of fetal haemoglobin (HPFH) and sometimes in β thalassaemia trait. It is occasionally raised in other situations (Table 1), but apart from sickle cell disease and feto-maternal haemorrhage (FMH), there is little clinical utility in measuring the Hb F in these other situations (Mosca et al., 2009).

 

The clinical effects of sickle cell disease can be reduced by using drugs such as hydroxyurea (hydroxycarbamide) which raise the Hb F level and measuring the Hb F level can then be clinically useful in helping to determine the appropriate dose regime. The assessment of the proportion of red cells of fetal origin is clinically useful in assessing the amount of FMH that has occurred and the medication to be given.

 

Assessing the proportion of cells that contain a high proportion of fetal haemoglobin (often called F cells) is also useful in the diagnosis of ‘classical’ deletional HPFH.

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