Laboratory Finding In Hereditary Spherocytosis

The different laboratory findings observed in patients with hereditary spherocytosis is summarized as follows.

Evidence of hemolysis includes reticulocytosis and indirect hyperbilirubinemia.

Hb Level:
The hemoglobin level usually is 6–10 g/dL, but it can be in the normal range.

Retic Count:
The reticulocyte percentage often is increased to 6–20%, with a mean of approximately 10%.

Absolute Values:
The mean corpuscular volume is normal, although the mean corpuscular hemoglobin concentration often is increased (36–38 g/dL RBCs).

Blood Film:
The RBCs on the blood film vary in size and include polychromatophilic reticulocytes and spherocytes. The spherocytes are smaller in diameter and appear hyperchromic on the blood film as a result of the high hemoglobin concentration. The central pallor is less conspicuous than in normal cells. Spherocytes may be the predominant cell or may be relatively sparse, depending on the severity of the disease, but they usually account for >15–20% of the cells when hemolytic anemia is present.

Bone marrow:
Erythroid hyperplasia is evident in the marrow aspirate or biopsy. Marrow expansion may be evident on routine roentgenographic examination.

Other Features :
Other evidence of hemolysis may include decreased haptoglobin and the presence of gallstones on ultrasonography.

Diagnosis:
The diagnosis of hereditary spherocytosis usually is established clinically from the blood film, which shows many spherocytes and reticulocytes, from the family history, and from splenomegaly.

Osmotic Fragilty Test:
The presence of spherocytes in the blood can be confirmed with an osmotic fragility test . The RBCs are incubated in progressive dilutions of an iso-osmotic buffered salt solution. Exposure to hypotonic saline causes the RBCs to swell, and the spherocytes lyse more readily than biconcave cells in hypotonic solutions.

This feature is accentuated by depriving the cells of glucose overnight at 37°C, known as the incubated osmotic fragility test. Unfortunately, this test is not specific for hereditary spherocytosis, and results may be abnormal in immune and other hemolytic anemias. A normal test result also may be found in 10–20% of patients.