Haptoglobin Migrates with Alpha-2 Globulin on Serum Protein Electrophoresis
Haptoglobin migrates with the alpha-2 globulin fraction on normal serum protein electrophoresis (SPEP). 1
Characteristics of Haptoglobin
Haptoglobin is an acute phase protein with several important physiological functions:
- Primary role: Binds free hemoglobin released during intravascular hemolysis to form a complex that is rapidly cleared from circulation 1, 2
- Secondary functions:
- Inhibits oxidative stress
- Inhibits prostaglandin synthesis
- Serves as a positive acute phase reactant during inflammation 1
Haptoglobin on Serum Protein Electrophoresis
When examining SPEP patterns:
- Haptoglobin consistently migrates within the alpha-2 globulin region 1, 3
- Different haptoglobin phenotypes can affect the appearance of the alpha-2 zone:
- Hp1-1 phenotype: Causes significant splitting of the alpha-2 globulin zone
- Hp2-1 phenotype: Causes moderate splitting of the alpha-2 globulin zone
- Hp2-2 phenotype: Does not cause splitting of the alpha-2 zone 1
Clinical Significance
Understanding haptoglobin's migration pattern on SPEP is important because:
- Changes in haptoglobin levels can affect the alpha-2 region appearance on SPEP
- Haptoglobin levels increase during:
- Haptoglobin levels decrease during:
- Hemolysis (due to consumption)
- Liver disease
- Malnutrition
- Certain allergic reactions 5
Potential Confounding Factors
When interpreting SPEP results, be aware that:
- In vitro hemolysis can cause splitting of the alpha-2 globulin zone, mimicking certain haptoglobin phenotypes 1
- Migration of monoclonal components (such as immunoglobulin free light chains) may also affect the alpha-2 region appearance 1
- SPEP has limited sensitivity for detecting small monoclonal proteins, making it essential to use complementary testing like serum immunofixation electrophoresis (SIFE) and serum free light chain assays 6
In summary, when analyzing SPEP patterns, haptoglobin is a key protein that migrates with the alpha-2 globulin fraction, and its levels and phenotype can provide valuable diagnostic information about various pathological conditions.