Table of Contents
What does increased hemoglobin F mean?
High levels of hemoglobin F may be seen in a rare condition called hereditary persistence of fetal hemoglobin. Hemoglobin S in moderate amounts can mean that sickle cell trait is present. Hemoglobin S in high amounts means sickle cell disease. Hemoglobin C in low amounts can mean that hemoglobin C trait is present.
What causes high HbF?
HbF is elevated in inherited conditions, such as hereditary persistence of HbF, hereditary spherocytosis, and thalassemia. The level of HbF is also increased in acquired states, such as pregnancy, aplastic anemia, thyrotoxicosis, hepatoma, myeloproliferative disorders, or hypoplastic myelodysplastic syndrome.
When does HbF change to HbA?
HbF, optimal for oxygen transport in utero, is progressively replaced by HbA from about 32-36 wk of gestation (1). This maturational phenomenon is clinically important and shows marked individual variation.
Why does HbF increase in thalassemia?
These data suggest that the high HbF levels in HbE/beta thalassemia, and other beta thalassemia syndromes, result from increased erythropoietin levels leading to bone marrow expansion, and possibly increased F-cell production, combined with ineffective erythropoiesis giving a survival advantage to F cells.
What causes hemoglobin F?
Hb F is often mildly to moderately elevated in sickle cell disease, aplastic anemia, acute leukemia, and myeloproliferative disorders such as juvenile myelomonocytic leukemia (JMML), hereditary spherocytosis, and alpha-thalassemia minor. It is commonly increased in hemoglobinopathies associated with hemolysis.
What is a fatal hemoglobin level?
Electrocardiographic changes associated with tissue hypoxia can occur at a hemoglobin level <5 g/dL in healthy adults. Studies show mortality and morbidity increase rapidly at levels <5.0 to 6.0 g/dL.
What happens if HbF is high?
A baby growing in the womb has high levels of HbF. The level of HbF usually drops to tiny amounts about 6 months after birth. In an adult or child, a higher level of HbF can mean you have a blood disorder. These include thalassemia, myeloid leukemia, and sickle cell anemia.
Which age is fetal hemoglobin HbF still present in the body?
It is produced at around 6 weeks of pregnancy and the levels remain high after birth until the baby is roughly 2–4 months old. Hemoglobin F has a different composition from the adult forms of hemoglobin, which allows it to bind (or attach to) oxygen more strongly.
What form of HB replaces HbF?
Shortly after the time of birth there is a switch from predominant expression of HbF to adult hemoglobin (HbA), which is mediated by a transcriptional switch in definitive erythroid progenitors from γ- to β-globin (Fig. 1). Figure 1.
Why HbF is replaced by HbA?
Blood transfusion with adult haemoglobin (HbA) replaces foetal haemoglobin (HbF). HbA has a lower affinity for oxygen than HbF and therefore leads to increased oxygen availability to the tissues including the retina.
What does F mean in blood test?
The full blood count (FBC) is one of the most commonly requested tests and provides important information about the kinds and numbers of cells in the blood: red blood cells, white blood cells and platelets. Abnormalities in any of these types of cells can indicate the presence of important medical disorders.
What causes hemoglobin F to be above 35%?
Heterocellular distribution is found in delta beta thalassemia, medication induced, and other causes of increased Hb F. When hemoglobin (Hb) F values are above 35%, most specimens show a homocellular pattern; this does not necessarily indicate hereditary persistence of fetal Hb (HPFH). Clinical correlation is needed.
What causes increase in Hb F in blood?
Hb F is also increased due to medications such as hydroxyurea, decitabine, and lenalidomide.
When does H emoglobin F begin to decline?
H EMOGLOBIN F (HbF, α 2 γ 2) accounts for up to 90% of the circulating hemoglobin at birth. Its synthesis starts to decline during the third trimester, and over the first year of life it is gradually replaced by adult hemoglobin, HbA (α 2 β 2 ).
When does hemoglobin F diminish in an adult?
More than 75% of the hemoglobin of the newborn is hemoglobin F (Hb F); it diminishes over a period of several months to adult levels, reducing to less than 2% by age 1 and less than 1% by age 2.