Haptoglobin (acronym: Hp) is an α2-glycoprotein and acute-phase protein. It is synthesized (produced) in the liver. Haptoglobin binds free hemoglobin (fHb) containing iron as a transport protein to form a haptoglobin-hemoglobin complex (HHK). Release of iron would result in the formation of reactive oxygen radicals, which exert a toxic effect. Due to genetic polymorphism (occurrence of multiple gene variants), haptoglobin occurs in three different phenotypes (appearances) (see under “Additional Notes”).
The process
Material needed
- Serum
Preparation of the patient
- Not necessary
Standard values
| Collective |
Norm | |
| Men | 25 years | 34-227 mg/dl |
| 50 years | 47-246 mg/dl | |
| 70 years | 46-266 mg/dl | |
| Women | 25 years | 49-218 mg/dl |
| 50 years | 59-237 mg/dl | |
| 70 years | 65-260 mg/dl | |
| Children | 12 months | 2-300 mg/dl |
| 10 years, male | 8-172 mg/dl | |
| 10 years, female | 27-183 mg/dl | |
| 16 years, male | 17-213 mg/dl | |
| 16 year, female | 38-205 mg/dl | |
Indications
- Diagnosis and progression of hemolytic diseases (hemolysis: dissolution of red blood cells).
Interpretation
Interpretation of increased values
- Acute and chronic inflammatory reactions
- Cholestasis (bile stasis)
- Iron deficiency anemia (anemia due to iron deficiency).
- Hodgkin’s disease (malignant neoplasm of the lymphatic system with possible involvement of other organs).
- Nephrotic syndrome – collective term for symptoms that occur in various diseases of the glomerulus (renal corpuscles); symptoms include: Proteinuria (excretion of protein with urine) with a protein loss of more than 1g/m²/body surface per day; Hypoproteinemia, peripheral edema (water retention) due to hypalbuminemia of < 2.5 g/dl in serum, hyperlipoproteinemia (lipid metabolism disorder) with LDL elevation.
- Rheumatoid arthritis
- Necrosis (death of single cells or cell clusters).
- Tumors
Interpretation of decreased values
- Intravascular (“within vessels”) hemolysis:
- Hemolytic anemias
- Hemoglobinurias (red coloration of urine due to hemoglobin).
- EBV infection (Epstein Barr virus infection).
- Pernicious anemia (anemia caused by a deficiency of vitamin B12 or, less commonly, folic acid deficiency).
- Artificial heart valves
- Synthesis disorder
- Acute and chronic liver disease
- Congenital haptoglobin deficiency, for example, in 30% of blacks in Nigeria; 1: 1,000 in Caucasians
- Malabsorption syndrome
Other notes
- Because haptoglobin is an acute-phase protein, assessment of serum haptoglobin levels should always be performed in combination with C-reactive protein (CRP). Acute disease associated with hemolysis may result in relatively unremarkable haptoglobin (Hp) levels (acute-phase: Hp ↑; hemolysis: Hp ↓).
- In extravascular (“outside of vessels“) hemolysis, a decrease in haptoglobin occurs only in hemolytic crises.
- Hemopexin (glycoprotein) is better than haptoglobin for assessing the extent of hemolysis. It binds hemin in a 1:1 molecular ratio and transports them to the liver, where they are broken down.
Phenotypes of haptoglobin and their normal values
| Phenotype | Occurrence | Normal values |
| Hp 1-1 | Most common type in Africa, South and Central America | 30-200 mg/dl |
| Hp 2-1 | Most common type among Asians | 40-200 mg/dl |
| Hp 2-2 | Most common type in central Europeans | 30-200 mg/dl |
