Genetic testing for thalassemia

What are the items needed for thalassemia gene testing?

A few days ago, a friend of mine had a marriage check-up and was found to have mild symptoms of thalassemia. Further examination was needed, but he didn't know what to check specifically, so he came to ask. I think some other friends may have similar questions, so let's talk about them here. There are several main laboratory tests related to thalassemia gene testing.

The main laboratory tests related to thalassemia are as follows: ① Red blood cell fragility test. ② Routine blood test (also called blood cell analysis). ③Hemoglobin electrophoresis, quantitative determination of hemoglobin A2 and quantitative determination of hemoglobin F. ④Peptide chain analysis. ⑤Thalassemia gene analysis.

The laboratory tests for thalassemia are briefly introduced below:

1. Red blood cell fragility test: The method is simple and easy to carry out, but the accuracy is not high. Most thalassemia patients will have abnormal results, but those with mild thalassemia and silent thalassemia genes may have normal results. This test can only indicate thalassemia but cannot diagnose it.

2. Routine blood test (also called blood cell analysis): County-level hospitals have automatic blood cell hemoanalyzers, which are very easy to do and inexpensive. It can completely replace the red blood cell fragility test and is more accurate than the red blood cell fragility test. This test can only indicate thalassemia, not make a diagnosis.

3. Hemoglobin electrophoresis, quantitative determination of hemoglobin A2 and quantitative determination of hemoglobin F: This test can confirm the diagnosis of severe and intermediate thalassemia (α and β). It can also confirm the diagnosis of mild β-thalassemia and silent β-thalassemia gene carriers, but cannot be diagnosed in a few people. This test cannot be used to diagnose mild α-thalassemia and silent α-thalassemia gene carriers, but it may provide a hint in a few cases.

4. Zeta chain detection: It is mainly used in clinical practice for the diagnosis of mild α-thalassemia. It was commonly used in the past, but because it requires highly toxic reagents in the experiment, it is harmful to the inspectors and also causes great pollution to the environment. It is now done using enzyme labeling method, which is more accurate than before, but it is better to do it in batches. A positive zeta chain can be clearly diagnosed as mild α-thalassemia (Southeast Asian deletion type).

5. Thalassemia gene analysis: Genetic analysis can replace all the above tests, but it is difficult to carry out in general hospitals due to the high requirements for equipment, laboratories, and technical personnel.

The most serious types of thalassemia genes include Hb Bart's fetal edema syndrome, major β-thalassemia and hemoglobin H disease. Although patients with silent or mild thalassemia do not have serious clinical symptoms, the abnormal α and β globin genes carried by the couple can be passed on to their offspring, sometimes with serious consequences. Therefore, premarital examination is necessary, especially the thalassemia gene test, which everyone must pay attention to.