Hemoglobin electrophoresis is a diagnostic technique that aims to identify the different types of hemoglobin that can be found circulating in the blood. Hemoglobin or Hb is a protein present in red blood cells responsible for binding to oxygen, allowing transport to tissues. Learn more about hemoglobin.
From the identification of the type of hemoglobin, it is possible to check if the person has any disease related to hemoglobin synthesis, such as thalassemia or sickle cell anemia, for example. However, in order to confirm the diagnosis, it is necessary to perform other hematological and biochemical tests.
What is it for
Hemoglobin electrophoresis is requested to identify structural and functional changes related to hemoglobin synthesis. Thus, it can be recommended by the doctor to diagnose sickle cell anemia, hemoglobin C disease and differentiate thalassemia, for example.
In addition, it can be requested with the aim of genetically advising couples who wanted to have children, for example, being informed if there is a chance that the child will have some type of blood disorder related to hemoglobin synthesis. Hemoglobin electrophoresis can also be ordered as a routine exam for monitoring patients already diagnosed with different types of hemoglobin.
In the case of newborn babies, the type of hemoglobin is identified through the heel prick test, which is important for the diagnosis of sickle cell anemia, for example. See which diseases are detected by the heel prick test.
How it is done
Hemoglobin electrophoresis is done by collecting a blood sample by a professional trained in a specialized laboratory, because the incorrect collection can result in hemolysis, that is, destruction of red blood cells, which can interfere with the result. Understand how blood is collected.
The collection must be done with the patient fasting for at least 4 hours and the sample sent for analysis in the laboratory, in which the types of hemoglobin present in the patient are identified. In some laboratories, it is not necessary to fast for collection. Therefore, it is important to seek guidance from the laboratory and the doctor about fasting for the exam.
The type of hemoglobin is identified by electrophoresis in alkaline pH (around 8.0 - 9.0), which is a technique based on the migration rate of the molecule when submitted to an electric current, with the visualization of bands of according to the size and weight of the molecule. According to the band pattern obtained, a comparison is made with the normal pattern and, thus, the identification of abnormal hemoglobins is made.
How to interpret the results
According to the presented band pattern, it is possible to identify the type of hemoglobin of the patient. Hemoglobin A1 (HbA1) has a higher molecular weight, so much migration is not noticed, while HbA2 is lighter, getting deeper into the gel. This band pattern is interpreted in the laboratory and released in the form of a report to the doctor and the patient, informing the type of hemoglobin found.
Fetal hemoglobin (HbF) is present in higher concentrations in the baby, however, as development occurs, HbF concentrations decrease while HbA1 increases. Thus, the concentrations of each type of hemoglobin vary according to age, and are usually:
| Hemoglobin type | Normal value |
| HbF |
1 to 7 days of age: up to 84%; 8 to 60 days of age: up to 77%; 2 to 4 months of age: up to 40%; 4 to 6 months old: up to 7.0% 7 to 12 months of age: up to 3.5%; 12 to 18 months of age: up to 2.8%; Adult: 0.0 to 2.0% |
| HbA1 | 95% or more |
| HbA2 | 1.5 - 3.5% |
However, some people have structural or functional changes related to hemoglobin synthesis, resulting in abnormal or variant hemoglobins, such as HbS, HbC, HbH and Barts' Hb.
Thus, from hemoglobin electrophoresis, it is possible to identify the presence of abnormal hemoglobins and, with the help of another diagnostic technique called HPLC, it is possible to check the concentration of normal and abnormal hemoglobins, which may be indicative of:
| Hemoglobin result | Diagnostic hypothesis |
| Presence of HbSS | Sickle cell anemia, which is characterized by a change in the shape of the red blood cell due to a mutation in the beta chain of hemoglobin. Know the symptoms of sickle cell anemia. |
| Presence of HbAS | Sickle cell trait, in which the person carries the gene responsible for sickle cell anemia, but does not show symptoms, however, it can pass this gene on to other generations: |
| Presence of HbC | Indicative of hemoglobin C disease, in which HbC crystals can be observed in the blood smear, especially when the patient is HbCC, in which the person has hemolytic anemia of varying degree. |
| Presence of Hb de Barts |
The presence of this type of hemoglobin indicates a serious condition known as hydrops fetalis, which can result in death of the fetus and consequently miscarriage. Learn more about fetal hydrops. |
| Presence of HbH | Indicative of Hemoglobin H disease, which is characterized by precipitation and extravascular hemolysis. |
In the case of sickle cell anemia diagnosis, the normal result is HbFA (that is, the baby has both HbA and HbF, which is normal), while the HbFAS and HbFS results are indicative of sickle cell trait and sickle cell anemia respectively.
The differential diagnosis of thalassemias can also be made by means of hemoglobin electrophoresis associated with HPLC, in which the concentrations of alpha, beta, delta and gamma chains are verified, verifying the absence or partial presence of these globin chains and, according to the result, determine the type of thalassemia. Learn how to identify thalassemia.
To confirm the diagnosis of any disease related to hemoglobin, other tests such as iron, ferritin, transferrin, in addition to a complete blood count, must be ordered. See how to interpret the blood count.
