Thalassemia and Hemoglobinopathy Comprehensive

The Thalassemia and Hemoglobinopathy Comprehensive test contains 1 test with 22 biomarkers.

Includes

• Hemoglobin A, Hemoglobin F, Hemoglobin A2 (Quant), Hemoglobin A2 Prime, Hemoglobin S, Hemoglobin C, Hemoglobin D, Hemoglobin G, Hemoglobin Lepore, Hemoglobin E, Hemoglobin Barts, Variant Hemoglobin, HPLC, Hemogram (Red Blood Cell Count, Hemoglobin, Hematocrit, MCV, MCH, MCHC, RDW), Ferritin and Interpretation
•  
• This is a reflexive profile. Additional testing, such as molecular tests, will be added at an additional charge, if indicated.
•  
• If results suggest sickling hemoglobin, Sickle Cell Screen will be performed at an additional charge (CPT code(s): 85660). 
•  
• If results suggest an unstable hemoglobin based on % of the variant and pattern seen on HPLC and Electrophoresis , Unstable Hemoglobin (Isopropanol) will be performed at an additional charge (CPT code(s): 83068).
•  
• If the hemogram shows microcytosis or decreased MCH or both and, there is no evidence of beta thalassemia (i.e., normal A2 and HbF), Alpha Globin common mutation analysis will be performed at an additional charge (CPT code(s): 81257). In consultation with the client, this test may also be performed (at an additional charge) in an individual with a normal hemogram for genetic counseling purposes as individuals with mild alpha thalassemia commonly have a normal hemogram and normal fractions.
•  
• If HPLC or CZE, point to an unidentified alpha globin variant, the sample will be sent for DNA sequencing and Alpha Globin Complete will be performed at an additional charge (CPT code(s): 81259).
•  
• If the genotyping results for the common deletions do not match the phenotype, Alpha Globin Gene Deletion or Duplication will be performed at an additional charge (CPT code(s): 81269) and Alpha Globin Complete will be performed at an additional charge (CPT code(s): 81259).
•  
• If a rare beta globin variant cannot be definitively identified by HPLC or CZE, Beta Globin Complete will be performed at an additional charge (CPT code(s): 81364).
•  
• If result suggests Hereditary persistence of fetal hemoglobin or Delta beta thalassemia or a beta thalassemia with negative beta globin sequencing, Beta globin gene dosage assay will be performed at an additional charge (CPT code(s) 81363).
•  
• Gamma globin gene sequencing or delta globin gene sequencing may be added at an additional charge, if clinically indicated. These tests are performed at an outside reference lab. Not applicable to CA and FL clients.
• If a reflex test is added, Genotype/phenotype review will be added at an additional charge (CPT code(s) 80500).

Clinical Significance

Thalassemia and Hemoglobinopathy Comprehensive Evaluation - Thalassemia and hemoglobinopathies are disorders related to hemoglobin pathophysiology. Although hemoglobinopathies and thalassemias are two genetically distinct disease groups, the clinical manifestations of both include anemia of variable severity and variable pathophysiology.
Thalassemias are group of autosomal recessive disorder of hemoglobin synthesis characterized by the reduction in the rate of synthesis of globin chain of one or more globin chain. The decreased synthesis of globin chain may result from gene deletion, non-sense mutation or mutation that affects the transcription or stability of mRNA products. Thalassemias are classified by the type and magnitude of decreased synthesis of the globin chain and severity of the clinical symptoms. The clinical manifestation ranges from mild anemia with microcytosis to fatal severe anemia.
In the alpha-thalassemias, there is absence or decreased production of beta-globin subunits, whereas in the beta- thalassemias, there is absent or reduced production of beta globin subunits. Rare thalassemias affecting the production of delta or gamma globin subunits have also been described but are not clinically significant disorders.
The beta-thalassemias can be sub-classified into those in which there is total absence of normal beta globin subunit synthesis or accumulation, the beta-zero thalassemias, and those in which some structurally normal beta globin subunits are synthesized, but in markedly decreased amounts, the beta-plus thalassemias. The alpha-thalassemia syndromes however, are usually caused by the deletion of one or more alpha globin genes and are sub-classified according to the number of alpha globin genes that are deleted (or mutated): one gene deleted (alpha-plus thalassemia); two genes deleted on the same chromosome or in cis (alpha-zero thalassemia); three genes deleted (HbH disease); or four genes deleted (hydrops fetalis with Hb Bart's).
Hemoglobinopathies results from the abnormal structure of One of the globin chains of the hemoglobin molecule (mutation of alpha and/or beta globin chain resulting in a variant form of Hemoglobin A). They are inherited single- gene disorders and in most cases, they are inherited as autosomal co-dominant traits. A large number (>800) of variants of hemoglobin (Hb) have been recognized. They are identified by capital letters (eg, Hb A or Hb S), or by the city in which the variant was first discovered (eg, Hb Koln).
Alpha chain variants usually form less than 25% of the total hemoglobin because the mutation typically occurs in one of the four genes that codes for alpha globin chain. For beta globin variants in the heterozygous state the variant forms more than 25% but less than 50% of the total hemoglobin. Ranked in order of relative frequency, these are: Hb S (sickle cell disease and trait), C, E, Lepore, G-Philadelphia, D-Los Angeles, Koln, Constant Spring, O-Arab, and others.
Most common beta globin variants include HbS, HbC, HbD, HbE and HbG. A mutation in one beta globin subunit results in a combination of variant and normal hemoglobin and denotes carrier or trait status, also known as the heterozygote state. Mutations in both beta globin subunits result in disease based on a homozygous expression such as sickle cell anemia (HbSS). Other diseases under sickle cell disease (SCD) are HbSE, HbSC and HbS beta-thalassemia.